Additions to the knowledge of the land snails of Sabah (Malaysia, Borneo), including 48 new species

Abstract We present reviews of the Sabah (Malaysia, on the island of Borneo) species of the following problematical genera of land snails (Mollusca, Gastropoda): Acmella and Anaglyphula (Caenogastropoda: Assimineidae); Ditropopsis (Caenogastropoda: Cyclophoridae); Microcystina (Pulmonata: Ariophantidae); Philalanka and Thysanota (Pulmonata: Endodontidae); Kaliella, Rahula, (Pulmonata: Euconulidae); Trochomorpha and Geotrochus (Pulmonata: Trochomorphidae). Next to this, we describe new species in previously revised genera, such as Diplommatina (Diplommatinidae); Georissa (Hydrocenidae); as well as some new species of genera not revised previously, such as Japonia (Cyclophoridae); Durgella and Dyakia (Ariophantidae); Amphidromus, and Trachia (Camaenidae); Paralaoma (Punctidae); Curvella (Subulinidae). All descriptions are based on the morphology of the shells. We distinguish the following 48 new species: Acmella cyrtoglyphe, Acmella umbilicata, Acmella ovoidea, Acmella nana, Acmella subcancellata, Acmella striata, and Anaglyphula sauroderma (Assimineidae); Ditropopsis davisoni, Ditropopsis trachychilus, Ditropopsis constricta, Ditropopsis tyloacron, Ditropopsis cincta, and Japonia anceps (Cyclophoridae); Diplommatina bidentata and Diplommatina tylocheilos (Diplommatinidae); Georissa leucococca and Georissa nephrostoma (Hydrocenidae); Durgella densestriata, Dyakia chlorosoma, Microcystina microrhynchus, Microcystina callifera, Microcystina striatula, Microcystina planiuscula, and Microcystina physotrochus (Ariophantidae); Amphidromus psephos and Trachia serpentinitica (Camaenidae); Philalanka tambunanensis, Philalanka obscura, Philalanka anomphala, Philalanka rugulosa, and Philalanka malimgunung (Endodontidae); Kaliella eurytrochus, Kaliella sublaxa, Kaliella phacomorpha, Kaliella punctata, Kaliella microsoma, Rahula delopleura, (Euconulidae); Paralaoma angusta (Punctidae); Curvella hadrotes (Subulinidae); Trochomorpha trachus, Trochomorpha haptoderma, Trochomorpha thelecoryphe, Geotrochus oedobasis, Geotrochus spilokeiria, Geotrochus scolops, Geotrochus kitteli, Geotrochus subscalaris, and Geotrochus meristorhachis (Trochomorphidae).


Introduction
Apart from a few revised groups (Vermeulen 1991(Vermeulen , 1993(Vermeulen , 1994Liew et al. 2009), the taxonomic structure supporting recent research on the terrestrial molluscs of Sabah, Malaysia (the Northeast part of the Island of Borneo), such as Clements et al. (2008); Liew et al. (2010); Schilthuizen et al. (2013), consists of an unpublished working guide assembled by the first author in 2005. It includes an outdated checklist of all the species occurring in Sabah, with short descriptions where necessary to distinguish between species, and illustrations of the most critical groups. The working guide contains numerous undescribed species, with informal species names. Recently, some of these informal names have found their way into the scientific literature and on to the electronic taxonomic media. This is undesirable. Therefore, we have decided to formally describe the new species present in the working guide. This should be seen as a first step in a process that will culminate into a comprehensive guide to the land snail fauna of Sabah. We present the new species of several critical genera within the framework of a concise review of those genera, in order to provide present researchers with an identification tool with our latest insights into the taxonomy of the local land snail fauna. We divide the species of the larger genera reviewed in informal groups, to facilitate the use of the reviews.
At present, the material available to us largely consists of dry specimens, generally extracted from soil samples gathered by the authors since 1986. The samples from Sabah have yielded close to 8000 lots in our combined collections. Therefore, the species are distinguished by shell characters only. We are aware of the shortcomings of these proceedings, but we feel that investigations into the Sabah snail fauna are better helped by describing the species now, rather than by waiting until we have preserved animals of a representative selection of the species.
The material studied derives from the following collections, indicated with abbreviations: BOR/MOL (BORNEENSIS collection, Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah), RMNH (Naturalis, the natural history museum of the Netherlands), and V (private collection J.J. Vermeulen, Leiden, the Netherlands).
The drawings were made by the first author, with the aid of a Wild M8 stereo microscope with a Camera Lucida device; the SEM images were made by the second author. Also, all BOR/MOL samples were identified by the second author. 1.10-1.36; number of whorls 4 1/8-5 7/8; height aperture 0.35-0.50 mm; width aperture 0.37-0.50 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone bedrock, at 0-700 m alt. Sabah: Interior Province, South part; East coast: from Kinabatangan River valley and further South. Also in Sarawak, Kalimantan. Endemic to Borneo.
Habitat in Sabah and distribution. Primary and secondary forest on limestone bedrock, often in caves. Alt. 0-500 m. Sabah: Interior; East coast. Also in Kalimantan Timur. Distribution: Philippines.
Cross diagnosis. The largest Acmella species in Sabah. Description. Shell minute, rather thin, translucent, white. Surface shiny. Spire conical with slightly convex sides to ovoid, apex (broadly) obtuse, whorls slightly to moderately convex, sometimes slightly shouldered. Sculpture. Spiral sculpture predominant. Radial sculpture: scattered, inconspicuous growth lines only, in some shells locally grading into slight, densely placed and regularly spaced riblets on the crests of the spiral threads. Spiral sculpture: densely placed and regularly spaced, very fine, low and wide threads with only very narrow grooves in between. Aperture obliquely ovate in outline, with a concave to slightly convex parietal side, transition from parietal to basal side rounded. Umbilicus open, narrow. Dimensions. Height 0.85-1.35 mm; width 0.80-1.00 mm; h/w 1.00-1.35; number of whorls 3 1/2-5; height aperture 0.40-0.55 mm; width aperture 0.40-0.50 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone bedrock, at 0-700 m alt. Sabah: Interior Province, South part; along the East coast from the Kinabatangan River valley Southwards. Also in Sarawak; Kalimantan Timur. Endemic to Borneo.
Cross diagnosis. Characterized among the Sabah species by the more or less ovoid outline of the shell.
Differs from A. minutissima (Maassen, 2000) (= Anaglyphula minutissima Maassen), from Sumatra, by the same character. In addition, the sculpture on the teleoconch is different: the spiral threads are much wider, leaving only very narrow grooves in between. The radial sculpture cuts into the crests of the spiral grooves.
Remarks. The index h/w is highly variable, and the umbilicus may be wider than in the illustrated shell.
Description. Shell minute, rather thin, somewhat translucent, white. Surface shiny. Spire conical with flat to slightly convex sides, apex somewhat narrowly obtuse, whorls (moderately) convex, sometimes slightly shouldered. Sculpture. Spiral sculpture predominant. Radial sculpture: scattered, inconspicuous growth lines, grading into inconspicuous, rather densely placed and regularly spaced riblets on the crests of the spiral threads. Spiral sculpture: densely placed and regularly spaced, very fine, low and wide threads with only a very narrow groove in between. Aperture obliquely ovate in outline, with a slightly concave to approx. straight parietal side, transition from parietal to basal side rounded. Umbilicus open, narrow. Dimensions. Height 1.19-1.30 mm; Remarks. Originally included in the Valloniidae, a Pulmonate family. Its position in the Caenogastropoda was established by  and Vermeulen and Whitten (1998), who found a thin, paucispiral operculum in A. whitteni , as well as in A. tiluana (Von Moellendorff, 1897   Description. Shell minute, rather thick, about opaque, pale corneous. Surface shiny. Spire conical with approx. flat or slightly concave sides, apex somewhat narrowly obtuse, whorls moderately convex. Sculpture consisting of radial ribs intersecting with about equally strong spiral threads, creating a pattern of rounded, sharply delineated depressions on the shell surface; locally this pattern is distorted, and around the periphery and below the suture the depressions more or less line up parallel to the growth lines; close to the aperture radial riblets and growth lines predominate. Aperture widely and obliquely ovate in outline, with a slightly concave parietal side, transition from parietal to basal side obtusely angular. Peristome thickened, with a slight lip on the inner side. Umbilicus open, narrow. Dimensions. Height c. 1.75 mm; width c. 1.45 mm; h/w c. 1.25; number of whorls c. 5; height aperture c. 0.80 mm; width aperture c. 0.70 mm.
Habitat in Sabah and distribution. Primary forest on limestone soil, at 100-300 m alt. Sabah: East coast, Baturong Hill. Also in Kalimantan Timur. Endemic to Borneo.
Cross diagnosis. The sculpture uniquely identifies the species among the Sabah snail fauna.
A. sauroderma shares the irregularly cancellate sculpture, with shallow pits, with A. cancellata Rensch, 1932, from Flores. It differs in having a higher spire (distinctly higher than wide) and evenly rounded whorls.

Family CYCLOPHORIDAE Gray
Short description. Shell small to very large, dextral, discoid to ovoid to conical. Last whorl with or without a pore near the aperture; on the inside with (Alycaeinae) or without a constriction. Sculpture absent, or inconspicuous to distinct spiral and/or radial sculpture present; periostracal sculpture often present. Aperture rounded to whorl edges. However, D. aenigmatica (Van Benthem Jutting, 1963) (Biak Island, Indonesia) and D. heterospirifera   (from Misool Island, Indonesia) are similar to our Bornean species in general terms, but have an operculum with very distinct, erect, calcareous whorl edges.
For the Borneo material we conclude that the species listed below generally differ from the ones included in Craspedotropis by Vermeulen, 1999 by having a wider umbilicus and a less distinct radial sculpture. Their shell morphology agrees well with species generally included in Ditropopsis, and we include them in that genus. Below, we list all the Sabah species present in the collections available to us.
We divide the genus into three informal groups.
Habitat in Sabah and distribution. Found in montane forest, in a sandstone rock crevice near a small stream in thick leaf litter, at 1100 m alt. Sabah: Upper Padas River. Endemic to Sabah.
Cross diagnosis. Uniquely identified among the Sabah species by the tubular, detached teleochonch.

Ditropopsis trachychilus Vermeulen, Liew & Schilthuizen, sp. n.
http://zoobank.org/DBF5C5C5-B845-4479-B2FE-44D0940DCD7D Figure 10 Holotype. Malaysia Description. Shell very small, rather thick, hardly translucent, pale greenish. Surface shiny. Spire rather high-conical. Radial sculpture: fine growth lines, locally grading into fine, densely placed riblets. Sculpture. Spiral sculpture on the last whorl: 4 cords: 1 supraperipheral and 1 peripheral, about equally wide, 1 basal; these all rather distinct; 1 umbilical, inconspicuous and located deep inside the umbilicus; next to these a fine spiral striation on the lower surface. This sculpture continuing up to about 0.8 mm from the peristome, to be replaced by densely and irregularly placed radial riblets with a periostracal crest. Aperture. Peristome simple, not expanded, parietal side slightly detached from the penultimate whorl, basal side rounded, hardly drawn out. Dimensions. Height c. 2.3 mm; width c. 2 mm; h/w c. 1.15; umbilicus measured over the basal spiral cord c. 25 % of the shell width; number of whorls c. 4 1/8; height aperture c. 0.8 mm; width aperture c. 0.8 mm.
Cross diagnosis. Similar to D. koperbergi, but shell higher conical. The distinctive sculpture near the aperture develops only when fully adult, as in other species of the genus.
D. gradata Moellendorff, 1896 andD. pusilla Quadras &Moellendorff, 1895, from the Philippines, have a similarly high spire and spiral cord distribution. Both species have a more rounded profile to the whorls.
Habitat in Sabah and distribution. Primary forest on sandstone and limestone soil, 400-1200 m alt. Sabah: scattered localities. Also in Kalimantan. Endemic to Borneo.
Cross diagnosis. D. koperbergi is characterized by its simple peristome: the aperture is not constricted, and there is no distinctive, rough sculpture close to it.
Elsewhere in Borneo, the conical spire and the angular whorl profile identify the species.
Description. Shell very small, rather thick, somewhat translucent, white to pale (yellowish) green. Surface shiny or glossy. Spire almost flat, but apex protruding, slightly oblique. Sculpture. Radial sculpture: fine growth lines, locally grading into fine, densely placed riblets. Spiral sculpture on the last whorl: 6 very distinct cords: 1 supraperipheral and 1 peripheral, the latter widest and widely projecting, 1 basal and 3 umbilical; next to these a fine spiral striation on the lower surface. Sculpture continuing up to the peristome, but close to the peristome distorted and partly obliterated by densely placed, low radial riblets and increasingly coarse spiral threads. Aperture. Peristome simple, not expanded, distinctly constricted in fully adult shells, parietal side attached to the penultimate whorl in fully adult shells, basal side angular, slightly to distinctly drawn out. Dimensions. Height 1.4-1.65 mm; width 2.5-2.8 mm; h/w 0.52-0.56; umbilicus measured over the basal spiral cord 33-37 % of the shell width; number of whorls c. 4; height aperture 0.7-0.9 mm; width aperture 0.8-0.9 mm.
Habitat in Sabah and distribution. Primary forest on limestone soil, rarely on sandstone, 0-600 m alt. Sabah: S.E. part. Also in Kalimantan, East part. Endemic to Borneo.  Cross diagnosis. Well characterized among Sabah Ditropopsis by the low, almost flat spire with only the apex protruding. In Kalimantan the Sabah form (illustrated) locally grades into series with relatively smooth, large shells and with the supraperipheral and umbilical ridges partly or entirely missing. Such shells look a little like D. imadatei and D. cincta, but have a flatter spire and a wider umbilicus.
Elsewhere, D. moellendorfii Boettger, 1891 and D. papuana E.A. Smith, 1897 have similarly flat shells, but the first has a double peristome, and the second a more rounded spire.
Habitat in Sabah and distribution. Primary and secondary forest. Predominantly on limestone soil, scattered records from sandstone, 0-1000 m alt. Sabah: South and S.E. part. Also in Sarawak; Brunei; Kalimantan (East part). Endemic to Borneo.
Cross diagnosis. Differs from D. koperbergi by the constricted aperture, with a distinct radial sculpture. Juvenile shells of D. constricta, without a fully grown aperture, have lower conical shells than D. koperbergi, with a wider umbilicus.
Remarks. The drawn specimen has relatively thick spiral cords, specimens with thinner cords occur.
Etymology. The name refers to the constricted peristome. Description. Shell very small, rather thick, somewhat translucent, corneous to brown. Surface shiny or glossy. Spire low-conical with convex sides, apex protruding, slightly oblique. Sculpture. Radial sculpture: fine growth lines, locally grading into fine, densely placed riblets. Spiral sculpture on the last whorl: 2 very distinct cords: 1 peripheral, widest and widely projecting, 1 basal; next to these a fine and inconspicuous spiral striation, particularly below the suture and around the basal cord. Sculpture continuing up to the peristome, but close to the peristome somewhat distorted because crossed by a few slightly more distinct growth lines. Aperture. Peristome simple, not expanded, parietal side attached to the penultimate whorl, basal side moderately angular and somewhat drawn out. Dimensions. Height 1.9-2.0 mm; width 2.5-2.7 mm; h/w 0.70-0.76; umbilicus measured over the basal spiral cord 40-48 % of the shell width; number of whorls 4-4 1/2; height aperture 0.8-0.9 mm; width aperture c.  Figure 15 Ditropis imadatei Habe, 1965: 117 Description. Shell very small, rather thick, somewhat translucent, white to pale greenish. Surface shiny or glossy. Spire conical with convex sides, apex somewhat protruding, hardly oblique. Sculpture. Radial sculpture: fine growth lines, locally grading into fine, densely placed riblets. Spiral sculpture on the last whorl: 5 cords: 1 peripheral, 1 basal, very distinct, and 2 much thinner and more inconspicuous umbilical cords; next to these a fine spiral striation locally present. Sculpture continuing up to the peristome. Aperture. Peristome double, the outer thickened and distinctly expanded, parietal side attached to the penultimate whorl in fully adult shells, basal side angular, distinctly drawn out; the inner peristome slightly protruding from the outer, slightly expanded, basal side only slightly angular and slightly drawn out. Dimensions. Height c. 2 mm; width 2.0-2.2 mm; h/w c. 0.9; umbilicus measured over the basal spiral cord 25-31% of the shell width; number of whorls c. 4 1/8; height aperture c. 1 mm; width aperture 1.0-1.2 mm.
Cross diagnosis. Uniquely identified among the Sabah species by the double peristome. Elsewhere, D. moellendorfi Boettger, 1891 (Maluku) has a double peristome, but a much flatter shell with more numerous spiral cords.

Genus Japonia Gould, 1859
Japonia Gould, 1859: 426. Diagnosis for the Sabah species. Shell small, white to pale corneous or pale greenish, usually marked with brown. Surface dull or shiny. Spire low to high-conical. Radial sculpture usually consisting of growth lines, locally grading into riblets. Spiral sculpture usually consisting of inconspicuous to distinct threads, sometimes with a peripheral keel. Peristome simple or double, expanded or not, with a notch in the angular corner. Height 4-12 mm. Umbilicus narrow to wide.
Cross diagnosis. The genus Leptopoma Pfeiffer, 1847 (Borneo species revised by Vermeulen 1999), is most similar. Japonia is distinguished by the presence of a small notch in the angular corner of the peristome.
Remarks. The Borneo species, numbering about 25, have not yet been revised. Nonetheless, we feel confident to describe one, highly distinctive, new species. Description. Shell small, rather solid, opaque, white to yellowish, with vaguely outlined pale brown radial blotches on the upper surface. Surface slightly shiny. Spire conical, top distinctly protruding, periphery sharply angular, whorls almost flat to slightly convex (in large specimens) above the periphery, slightly convex below; transition from basal to umbilical area somewhat less distinctly angular than the periphery. Whorls not channeled towards the suture. Sculpture. Radial sculpture: rather distinct, irregular growth lines, grading into similar radial riblets. Spiral sculpture on the last whorl: 1 distinct peripheral thread, 1 distinct basal thread, above the peripheral thread slight and inconspicuous spiral striation, below slightly more distinct striation, in the umbilical region still more distinct striation, grading into very fine, densely placed, thin threads; penultimate whorl with 1 distinct peripheral thread, just above the suture. Aperture subcircular, slightly angular on the palatal side. Peristome double, the inner hardly reflected, a rim which slightly protrudes from the outer; the outer peristome moderately reflected, somewhat concave. Dimensions. Height 4.7-6.2 mm; width 5.6-7.1 mm; h/w 0.84-0.88; umbilicus 0.7-1.0 mm wide, u/w 0.11-0.13; number of whorls 4 7/8-5 5/8; height aperture 2.5-2.8 mm; width aperture 2.7-3.5 mm. Periostracum without hairs.

Japonia anceps
Habitat in Sabah and distribution. Secondary forest on limestone bedrock. Alt. c. 500 m. Sabah: Crocker Range, Laing Cave near Keningau only. Endemic to Sabah.
Cross diagnosis. Shares the angular periphery and the whorls which are only slightly convex above and below with J. hyalina Junau, 2007, andJ. ditropis Vermeulen &Junau, 2007, both from Sarawak. It differs from both by its larger size (shell height 4.7-6.2 mm, versus 2.0-3.5 mm), the presence of brown blotches on on the shell, as well as by the less conspicuous spiral sculpture apart from the peripheral and basal thread.
Etymology. The name refers to the fact that the upper and lower surface of the last whorl are about equally convex [anceps (L.) = with two faces].

Family DIPLOMMATINIDAE Pfeiffer
Short description. Shell (very) small, dextral or less frequently sinistral, ellipsoid to ovoid to conical, or cylindrical. Last whorl without a pore near the aperture; on the inside with a constriction. Coiling axis changing direction one to several times during development, often resulting in (partly) detached whorls. Sculpture: usually a distinct radial sculpture, spiral sculpture subordinate; rarely with spiral sculpture only, or without sculpture. Aperture rounded to somewhat angular above; peristome (distinctly) thickened. Umbilicus closed, or open, narrow. Operculum corneous, paucispiral (Family description based on Webster et al. 2012;Vermeulen 1991;Yamazaki 2013).
Habitat and distribution. Rock and soil foragers, frequently associated with limestone substrates. Asia (from India, China, Japan Southwards) to Australia, and Oceania.

Genus Diplommatina Benson, 1849
Diplommatina Benson 1849: 193. Remarks. The Borneo species of Diplommatina have been revised in Vermeulen (1993). We add two new species. Both display a very unusual character in the genus apertural teeth on the parietal side and in the angular corner.
Diplommatina bidentata Vermeulen, Liew & Schilthuizen, sp. n. http://zoobank.org/F899243D-677B-410B-91ED-8227C3410E2A Figure 17 Holotype. Malaysia Description. Shell dextral, conical, with the last whorl or the last two whorls widest; sides flat or slightly convex. Suture impressed. Constriction level with the parietal side of the peristome, with 1 parietalis which continues as a lamella down to the aperture, 1 longitudinal palatalis slightly to the left of the parietal peristome, 1 transversal palatalis, 1 columellaris which continues as a lamella down to the aperture. Tuba 7/8 whorl. Sculpture. Radial ribs straight, distinct, rather low, rather wide, rather densely placed (7-11 ribs/0.5 mm on the penultimate whorl). Spiral striation present, inconspious, fine and dense. Aperture hardly tilted with regard to the coiling axis; columellaris large, slightly downwards directed; the distal end of the parietalis visible on the parietal side as a tooth. Peristome double, expanding; palatal side only slightly sinuous, without edge; basal side without edge; basal edge not sinuous; outer peristome not or hardly expanding beyond the inner; inner peristome with a palatal lip, free and erect on the columellar side, expanding on the parietal side. Umbilicus open, narrow. Dimensions. Height 1.9-2.3 mm; width 1.00-1.25 mm; umbilicus 0.05-0.20 mm wide; number of whorls 6-6 3/4; height and width aperture 0.25-0.30 mm.
Habitat in Sabah and distribution. (Disturbed) primary forest on limestone bedrock, at c. 100 m alt. Sabah: East coast, Baturong Hill only. Endemic to Sabah.
Cross diagnosis. Uniquely identified by the parietal lamella, which runs over the full length of the tuba and which is visible as a pearietal tooth deep in the aperture.
In Vermeulen (1993) it keys out next to D. cacuminulus Vermeulen, 1993. Yet it seems most similar to D. toretos Vermeulen, 1993; it shares the open umbilicus with this species.
Etymology. The name refers to the two teeth in the aperture [bidentata (L.) = with two teeth].
Description. Shell dextral, fusiform, with the penultimate whorl widest. Suture impressed. Constriction level with the angular edge of the peristome, or up to 1/8 whorl beyond this point, towards the apex, with 1 parietalis, 1 longitudinal palatalis, 1 transversal palatalis, 1 columellaris which continues as a lamella down to the aperture. Tuba 1-1 1/8 whorl. Sculpture. Radial ribs straight, distinct, rather low, narrow, rather densely placed (6-9 ribs/0.5 mm on the penultimate whorl). Spiral striation present, rather distinct, moderately spaced. Aperture hardly tilted with regard to the coiling axis; columellaris large, patent; a second conical, obtuse tooth present on the palatal side, just below the angular edge. Peristome double, expanding; palatal side sinuous, with or without a slight edge; basal side without edge; basal edge not sinuous; outer peristome somewhat expanding beyond the inner; inner peristome with a palatal lip, free and erect on the columellar side, somewhat expanding on the parietal side. Umbilicus closed. Dimensions. Height 1.75-2.05 mm; width 0.95-1.15 mm; number of whorls 6-6 1/4; height aperture 0.30-0.40 mm; width aperture 0.35-0.45 mm.
Habitat in Sabah and distribution. Found in primary forest on limestone soil. Alt. 900-1000 m. Sabah: Gunung Trusmadi. Endemic to Sabah.
Cross diagnosis. Uniquely identified among Sabah Diplommatina species by the distinct, conical, obtuse tooth on the palatal peristome, close to the angular edge.

Family HYDROCENIDAE Troschel
Short description. Shell (very) small, dextral, ellipsoid to ovoid to conical. Last whorl without a pore near the aperture, on the inside without a constriction. Sculpture absent, or inconspicuous to distinct spiral and/or radial sculpture present, often fused to nodular structures. Aperture rounded to somewhat angular above; peristome usually not thickened. Umbilicus usually covered by a thickened callus, an extension of the peristome. Operculum calcareous, paucispiral, with a central calcareous peg projecting from the inner surface (Family description adapted from Barker 2001;Kobelt 1876;Suter 1913;Herbert and Kilburn 2004;Thompson and Dance 1983).
Habitat and distribution. Widespread in humid terrestrial environments, often associated with limestone habitats. Palearctis, Africa, but most diverse in Southeast Asia to Australia and Oceania.
Remarks. The family is poorly known and has not been revised in the past 140 years and as a consequence, the status of the various genus names (including Georissa) is uncertain.

Genus Georissa Blanford, 1864
Georissa Blanford, 1864: 463. Remarks. Thompson and Dance (1983) revised the Borneo species. We add two more.  Description. Shell minute, rather solid, translucent, white; spire conical with convex sides to approx. ovoid; apex rounded. Surface with a silky luster. Whorls moderately convex, rounded; last whorl somewhat more narrowly rounded to slightly angular at the periphery, rounded below. Protoconch minutely rugulose. Teleoconch: radial sculpture consisting of growth lines, locally grading into low, thin riblets at irregular intervals. Spiral sculpture: rather distinct, somewhat spaced, fine, low, thin, rounded spiral threads, on the last whorl present above the periphery, but absent in a narrow area just below the suture. Aperture semi-elliptic, with the parietal side approx. straight or slightly convex; peristome widely extended on the parietal side, not reflected elsewhere, free on the columellar side. Umbilicus open, rimate, a narrow slit underneath the reflected columellar peristome. Dimensions: Height 0.70-1.05 mm; width 0.65-1.00 mm; number of whorls 2 1/4-3; height aperture 0.35-0.50 mm; width aperture 0.35-0.45 mm.

Georissa leucococca
Habitat in Sabah and distribution. Primary and secondary forest on limestone bedrock. Alt. up to c. 500 m. Sabah: infrequent, a few localities only. Also in Sarawak. Endemic to Borneo.  Cross diagnosis. The small size, hardly over 1 mm high at 3 whorls, characterizes the species. Georissa gomantongensis E.A. Smith, 1893, has a similar spiral sculpture. Apart from being larger, it has orange to yellow shells and a nodular uppermost spiral thread, situated close to the suture.
The name refers to the white shell [leucos (Gr.) = white; coccos (Gr.) = kernel].  Description. Shell minute, solid, opaque or nearly so, orange to white; spire conical with convex sides; apex rounded. Surface with a silky luster. Whorls distinctly convex, rounded; last whorl rounded at the periphery. Protoconch minutely rugulose.

Georissa nephrostoma
Teleoconch: radial sculpture in some specimens consisting of growth lines, only locally somewhat raised, in others consisting of densely placed, inconspicuous to rather distinct, low and rather flat ridglets with narrow, shallow grooves in between. Spiral sculpture: virtually absent in some specimens, in others consisting of densely placed to somewhat spaced, very fine, shallow grooves cutting into the raised elements of the radial sculpture, but sometimes most conspicuous in between the radial riblets on the apical whorls. Aperture reniform, with the parietal side distinctly concave; peristome extended on the parietal side, not reflected elsewhere, embedded in the shell surface on the columellar side. Umbilicus closed. Dimensions: Height 1.35-1.60 mm; width 0.90-1.15 mm; number of whorls 2 3/4-3 1/2; height aperture 0.60-0.65 mm; width aperture 0.50-0.55 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone bedrock. Alt. up to c. 100 m. Sabah: Lower Kinabatangan valley only. Endemic to Sabah.
Cross diagnosis. Most similar to G. similis E.A. Smith 1893; distinguished by the deeply concave parietal peristome, giving the aperture a kidney-shaped outline. In G. similis the parietal side of the aperture is usually straight or slightly convex, seldomly a little concave. The sculpture of G. nephrostoma is on average less distinct than in G. similis, but both species include series of almost smooth specimens.

Clade: PULMONATA Cuvier
Family ARIOPHANTIDAE Godwin Austen Short description. Snails or semi-slugs. Shell (very) small to very large, dextral or sinistral, (low-)conical, ellipsoid, lenticular or discoid; semi-slugs with a (partly) reduced shell. Sculpture absent, or inconspicuous (rarely more distinct) spiral and/ or radial sculpture present. Aperture without teeth or lamellae, peristome usually thin and not reflected. Umbilicus closed or open, narrow (Family description adapted from Baker (1941), andSolem (1966). In contrast to our earlier paper, Liew et al. 2009, we here include the Dyakiinae in Ariophantidae, rather than treating them as a separate family).
Habitat and distribution. Generally forest species found on leaf litter and vegetation. Throughout South, East, and Southeast Asia, and Oceania, with a few species circumtropically introduced.   Description. Shell small, membranous, leathery with only a thin calcareous layer on the inside, somewhat translucent, greenish or brownish, low-conical with slightly concave sides; apex narrowly rounded. Surface shiny. Whorls convex, rounded, suture impressed. Protoconch approx. smooth. Teleoconch, radial sculpture: irregularly spaced, somewhat raised growth lines, locally grading into some very fine, inconspicuous, densely placed riblets. Spiral sculpture: above the periphery with very fine, wavy, densely placed, shallow grooves. Peristome not reflected. Umbilicus closed. Dimensions: Height up to 5.5 mm; width up to 6.2 mm; diameter of the first three whorls c. 0.85 mm, c. 1.75 mm, c. 3.7 mm respectively; number of whorls up to c. 3 3/4, height aperture up to 3.8 mm; width aperture up to 3.5 mm. Habitat in Sabah and distribution. Primary forest on sandstone or granodiorite bedrock. Alt. 2400-2700 m. Sabah: Mount Kinabalu. Endemic to Sabah.

Genus
Cross diagnosis. We assume this is the shell of an ariophantid semi-slug. Among the genera already reported from Borneo, it fits best in Durgella, Blanford, with regard to the general shell shape and the number of whorls. It differs from D. hosei Godwin Austen, 1891, from Sarawak, as well as from continental Asiatic species listed in Godwin Austen (1908: 213), Godwin Austen (1916: 555), and Solem (1966: 49) by having a low-conical spire with slightly concave sides, as well as by the fine and dense spiral striation.
Remarks. Only damaged material was available to us, with some dried remnants of the animal.

Genus Dyakia Godwin Austen, 1891
Dyakia Godwin Austen, 1891: 29.  Description. Shell medium-sized, very thin, translucent, pale yellowish green, conical with slightly concave (juveniles) to slightly convex (adults) sides; apex narrowly rounded. Surface glossy. Whorls: top whorls moderately convex, outer whorls flat above and convex below the periphery, periphery pinched and sharply keeled. Protoconch sculpture: a few flat radial folds, no other sculpture. Teleoconch, radial sculpture: first whorls slightly crenellated immediately below the suture, all whorls with more or less regularly spaced, slightly raised, weak growth lines, shell surface, particularly on the last whorl, distinctly undulated following the growth lines. Spiral sculpture absent, some shells with a inconspicuous spiral undulation on the last whorl. Peristome not reflected, not drawn out into a spur at the periphery. Umbilicus closed. Dimensions: Height up to 14 mm; width up to 32 mm; diameter of the first three whorls 1.9-2.1 mm, 3.5-4 mm, 8.0-8.3 mm respectively; number of whorls up to c. 4, height aperture up to 10.5 mm; width aperture up to 14.0 mm. Animal (pale) green including the tentacles, shining through the shell a bright green. Cross diagnosis. Very similar to Dyakia moluensis Godwin Austen, 1891, the shell differs by being very thin, by having a somewhat higher spire, and a markedly undulate upper surface, by absence of any colour markings, and by absence of a fine, somewhat spaced spiral striation on the upper and lower surface. For comparison, we also provide illustrations of D. moluensis ( fig. 23).
Adult shells of Rhinocochlis nasuta (Metcalfe, 1851) differ by having the palatal side of the peristome drawn out into a tapering, slightly backwards curved beak. Juvenile shells without the beak are very similar to Dyakia chlorosoma, but differ by the presence of a fine, somewhat spaced, spiral striation. The animal of R. nasuta is green, with somewhat yellowish to orange red tentacles.
Etymology Diagnosis for the Sabah species. Shell minute or very small, thin, lenticular, inflatedlenticular to depressed-ovoid; spire almost flat to moderately elevated. Surface shiny or glossy. Sculpture very fine, hardly prominent. Umbilicus open but very narrow, to closed, often partly or entirely covered by a minute, triangular spur protruding from the columellar corner of the peristome; this spur lacking or inconspicuous in juveniles. Dimensions: Width of adult shells 1.7-3.6 mm.
Remarks. The genus Microcystina includes small (up to 3.6 mm wide) species with lenticular (depressed ovoid in M. physotrochus) shells. Invariably, the shell surface seems smooth at a first impression, any sculpture present on the shells is very fine and inconspicuous. This distinguishes the smaller species of Microcystina (particularly M. sinica) from sympatric, yet undescribed Charopa species (Charopidae), which have lenticular, minute shells (width of adult shells 0.9-1.9 mm) with a much more conspicuous sculpture. In several Microcystina species the umbilicus is partly or entirely covered by a minute, triangular spur protruding from the columellar corner of the peristome.
Borneo Macrochlamys and Everettia (Ariophantidae), and Helicarion (Helicarionidae) may have similarly shaped shells, including the inconspicuous sculpture, but they are larger (width of adult shells 8 mm or more).
Placement of Microcystina into the family Ariophantidae follows Schileyko (2003). We provide a review of the Sabah species of Microcystina. We divide the genus into two informal groups.
Habitat in Sabah and distribution. Rainforest, periodically dry, shrubby woodland, coastal woodland, secondary forest and other degraded vegetation; on limestone, sandstone and granitic soil, up to 3500 m alt. Sabah: common and widespread. Also in Brunei; Sarawak; Kalimantan. Endemic to Borneo.
Cross diagnosis. Characterized among the Borneo Microcystina species with white shells by a complete lack of spiral striation. Usually it is also larger and has more rapidly expanding whorls.
Elsewhere, Lamprocystus vitreiformis Von Moellendorff, 1897, from Sumatra, Java, and Bali (see Vermeulen and Whitten 1998: 118) is most similar; M. microrhynchus is characterized by the minute spur protruding from the columellar corner of the peristome and covering the umbilicus. M. chionodiscus , from Bali (see Vermeulen and Whitten 1998: 115), has the first whorl consistently smaller (diameter 0.4-0.5 mm) than M. microrhynchus.
Etymology. The name refers to the spur covering the umbilicus [mikros (Gr.) = small; rhynchos (Gr.) = beak]. Description. Shell very small, (rather) thin, almost opaque or slightly translucent, white, lenticular; spire almost flat to moderately elevated. Surface with a silky luster. Whorls slightly convex. Protoconch with inconspicuous, widely spaced, continuous, shallow, vaguely outlined spiral grooves, as well as with fine, widely spaced, shallow radial riblets towards the teleoconch. Teleoconch: upper surface with very fine, widely spaced, continuous, moderately raised, sharply outlined spiral threads; lower surface with equally fine, widely spaced, shallow grooves. This sculpture is sometimes rather distinct, sometimes inconspicuous and patchy. Radial sculpture teleoconch: growth lines inconspicuous, in some specimens locally grading into irregularly and rather densely placed to widely spaced, shallow grooves. Umbilicus closed by a callous extension of the columellar corner of the peristome, the same callus also narrowing the aperture on the columellar side. Dimensions: Height up to 1.5 mm; width up to 2.5 mm; diameters of the first three whorls 0.5-0.6 mm, 0.9-1.0 mm, 1.2-1.4 mm respectively; number of whorls up to 4 1/2; height aperture up to 1.0 mm; width aperture up to 1.4 mm.

Microcystina callifera
Habitat in Sabah and distribution. Coastal woodland on limestone soil. Sabah: Islands: Mantanani Group and Banggi Island. Endemic to Sabah.
Cross diagnosis. Uniquely identified within Microcystina by the callus on the columellar side of the aperture. Substantial series of shells all have this callus, rendering the possibility of malformation unlikely. The spiral sculpture is usually more distinct, and more widely spaced than in M. striatula.
Etymology. The name refers to the callus in the aperture. Description. Shell very small, thin, almost (slightly) translucent, white, lenticular; spire almost flat to slightly elevated. Surface with a silky luster. Whorls slightly to moderately convex. Protoconch with a very fine (hardly visible at 40 times magnification), densely placed, continuous, shallow, vaguely outlined spiral striation, and sometimes with fine, moderately spaced, shallow radial grooves towards the teleoconch only. Teleoconch with very fine (just visible at 40 times magnification) only slightly spaced, continuous, shallow, rather vaguely outlined spiral grooves on the upper surface; similar, but more densely placed grooves on the lower surface. This spiral sculpture is inconspicuous and patchy in some shells. Radial sculpture teleoconch: inconspicuous growth lines mainly, sometimes a few scattered, slight grooves. Umbilicus open, narrow, inner wall with an obtuse periomphalic edge; umbilical region distinctly concave. Dimensions: Height up to 1.1 mm; width up to 1.9 mm; diameters of the first three whorls 0.4-0.5 mm, 0.8-0.9 mm, 1.4-1.5 mm respectively; number of whorls up to 3 3/4; height aperture up to 0.8 mm; width aperture up to 1.0 mm.

Microcystina striatula
Habitat in Sabah and distribution. Rainforest, seasonally dry coastal forest and shrubby forest on limestone bedrock, up to 1000 m alt. Sabah: scattered localities; less common than M. microrhynchus. Also in Kalimantan. Endemic to Borneo. Cross diagnosis. Differs at first sight from M. microrhynchus by the presence of a fine spiral striation, giving the shell a soft, silky shine rather than a high gloss. Next to that, the umbilical area is more distinctly concave.
Elsewhere, M. chionodiscus , from Bali, is similar, but M. striatula has a more distinct spiral striation.
Remarks. SEM images at 400 times magnification show that the areas in between the spiral grooves on the upper surface of the teleoconch have a 'welded' appearance.
Etymology. The name refers to the sculpture [striatula (L.) = finely striated].   Description. Shell minute, thin, somewhat translucent, pale yellowish to pale corneous, lenticular; spire moderately elevated, conical with a rounded apex. Surface moderately glossy, or with a silky shine. Whorls moderately convex. Protoconch with a fine, moderately spaced spiral striation consisting of rows of minute pits (barely visible at 40 times magnification) which are arranged in a reticulate pattern, sometimes traces of radial riblets (barely visible at 40 times magnification). Teleoconch: Spiral sculpture sometimes approx. absent or very fine (just visible at 40 times magnification), rather widely spaced, continuous, shallow, rather sharply outlined grooves present locally or over the entire shell. Radial sculpture teleoconch: inconspicuous growth lines, next to these inconspicuous to distinct, well-spaced to densely placed shallow grooves, often at irregular intervals. Umbilicus closed, or open and very narrow; columellar side of the peristome somewhat thickened but not covering the umbilicus; umbilical region slightly concave. Dimensions: Height up to 1.1 mm; width up to 1.7 mm; diameters of the first three whorls 0.3-0.5 mm, 0.5-0.8 mm, 0.8-1.3 mm respectively; number of whorls up to 4 18; height aperture up to 0.9 mm; width aperture up to 0.9 mm.

Microcystina sinica
Habitat in Sabah and distribution. Primary and secondary forest, coastal woodland on limestone, sandstone and volcanic bedrock, up to 1100 m alt. Elsewhere also in more severely degraded environments such as Imperata grass fields. Sabah: rather common in East Sabah, scattered localities in West Sabah. Also in Sarawak; Kalimantan. Distribution: widespread, from South China to Java; Eastwards to Irian Jaya.
Cross diagnosis. Shares the small size, slowly expanding whorls, and pitted protoconch with M. muscorum; it differs by having a continuous spiral striation on the teleoconch. Shells entirely without spiral striation can be distinguished by the colour, as well as by the absence of shallow, widely spaced radial grooves, as occur in M. muscorum.
M. striatula and M. gratilla have more rapidly expanding whorls, and have a flatter shell; M. striatula also has a white shell. Description. Shell very small, thin, translucent, pale yellowish green to yellowish brown, approx. lenticular; spire moderately elevated, conical with a rounded apex. Surface shiny, glossy below. Whorls moderately to distinctly convex. Protoconch without spiral sculpture; with fine, densely placed, low radial riblets towards the teleoconch, but slightly coarser than on the teleoconch. Teleoconch: Spiral sculpture above the periphery absent or inconspicuous, below the periphery with numerous fine, well-spaced, continuous, shallow, rather vaguely outlined grooves. Radial sculpture teleoconch: above the periphery with very fine, very densely and regularly placed, low riblets; below the periphery with some irregularly spaced growth lines only. Umbilicus open, narrow; columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 1.4 mm; width up to 2.3 mm; diameters of the first three whorls 0.5-0.6 mm, 0.8-1.0 mm, 1.4-1.6 mm respectively; number of whorls up to 4 1/4; height aperture up to 1 mm; width aperture up to 1.2 mm.
Cross diagnosis. Uniquely characterized within Group 2 by the fine and dense radial ribbing above the periphery.
Remarks. The description includes extralimital material as well. The Kinabalu material has slightly coarser radial riblets than the type.  Description. Shell very small, thin, translucent, yellowish brown, discoid-lenticular; spire almost flat. Surface glossy. Whorls moderately convex. Protoconch with 7-10 very fine, widely and regularly spaced spiral grooves. Teleoconch: very fine, widely and sometimes irregularly spaced spiral grooves on the upper and lower surface; these sometimes (partly) absent on the outer whorls. Radial sculpture teleoconch: scattered, inconspicuous growth lines; very slight, irregularly spaced folds just below the suture. Umbilicus open, narrow; columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 1.5 mm; width up to 2.6 mm; diameters of the first three whorls 0.7-0.8 mm, 1.2-1.3 mm, c. 2.3 mm respectively; number of whorls up to 3 1/8; height aperture up to 1.2 mm; width aperture up to 1.4 mm.

Microcystina planiuscula
Habitat in Sabah and distribution. Primary forest on limestone soil, 1600-1700 m alt. Sabah: Mt. Trusmadi only. Endemic to Sabah. Cross diagnosis. Identified by the distinctly more rapidly expanding whorls than in any other species in Group 2.
Etymology. The name refers to the shell shape [planiusculus (L.) = somewhat flattened]. Figure 34 Lamprocystis appendiculata  Description. Shell very small, thin, somewhat translucent, brown, lenticular; spire slightly to moderately elevated, conical with a rounded apex. Surface glossy. Whorls slightly convex. Protoconch with 6-10 very fine, well-spaced, continuous, shallow spiral grooves. Teleoconch: very fine, moderately to widely spaced, continuous, shallow, rather vaguely outlined spiral grooves on the top whorls, in adults usually absent on the last whorl above the periphery, but more frequently present, more densely placed, below the periphery. Spiral sculpture rarely entirely absent. Radial sculpture teleoconch: inconspicuous growth lines, a few irregularly spaced, very slight grooves. Umbilicus partly or entirely covered by a minute, semi-elliptic to triangular spur protruding from the columellar corner of the peristome; this spur often less conspicuous in juveniles. Dimensions: Height up to 1.9 mm; width up to 3.3 mm; diameters of the first three whorls 0.5-0.6 mm, 0.9-1.2 mm, 1.5-1.9 mm respectively; number of whorls up to 4 3/4; height aperture up to 1.3 mm; width aperture up to 1.9 mm.

Microcystina appendiculata (Von Moellendorff, 1893)
Habitat in Sabah and distribution. Primary and secondary forest on limestone and sandstone soil, up to 1400 m alt. Sabah: common in East Sabah, scattered lo calities in West Sabah. Distribution: Philippines (Palawan, Leyte).
Cross diagnosis. The only Sabah species within group 2 of Microcystina with a peristome extension covering the umbilicus. Similar to M. planiuscula, but with less rapidly expanding whorls, and with a finer spiral striation. Juveniles with an inconspicuous spur on the columellar side of the peristome can be distinguished from M. physotrochus by the lack of radial riblets on the protoconch and by with the flat, not convex, sides of the spire.
M. cavernae Godwin Austen, 1891, from Sarawak, has a shell of similar shape and colour; it differs in lacking the columellar spur.  Description. Shell very small, thin, translucent, straw yellow to brown, approx. lenticular; spire moderately elevated, conical with a rounded apex. Surface shiny. Whorls moderately convex. Protoconch with a fine, moderately spaced spiral striation consisting of rows of minute, rather sharply outlined pits which are arranged in a reticulate pattern towards the teleoconch; with or without patches of fine, densely placed riblets. Teleoconch: above the periphery with a very fine (just visible at 40 times magnification), dense and regularly spaced spiral striation, the striae consisting of rows of disconnected or partially connected, minute, rather deep, sharply outlined pits (best visible in tangential light); below the periphery the pits are sometimes more or less connected to continuous grooves. Spiral sculpture sometimes absent on the teleoconch. Radial sculpture teleoconch: inconspicuous growth lines, next to these with inconspicuous to distinct, well-spaced to densely placed, very shallow grooves, often at irregular intervals. Umbilicus open, narrow, columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 1.9 mm; width up to 3.1 mm; diameters of the first three whorls 0.3-0.5 mm, 0.6-0.9 mm, 1.1-1.5 mm respectively; number of whorls up to 5 1/4; height aperture up to 1.2 mm; width aperture up to 1.5 mm.

Microcystina muscorum
Habitat in Sabah and distribution. Primary and secondary forest, coastal woodland on limestone and sandstone soil, up to 2100 m alt. Sabah: rather common in East Sabah, only few localities in West Sabah. Distribution: Laos; Peninsular Malaysia; Sumatra; Java; Bali.
Cross diagnosis. Usually well-characterized by the spiral striation consisting of minute pits. Rare populations (one in Sabah) lack this striation on the teleoconch. On the protoconch, however, the pits are always present, which serves to distinguish M. muscorum from M. gratilla.
M. sinica has a similarly pitted protoconch, see under that species. Description. Shell very small, thin, translucent, yellowish brown to brown, lenticular; spire almost flat to moderately elevated, conical with a rounded apex. Surface glossy. Whorls moderately convex. Protoconch: spiral striation absent, with or without a few inconspicuous, scattered radial riblets towards the teleoconch. Teleoconch: with or without traces of very fine (only just visible at 40 times magnification), widely and somewhat irregularly spaced, shallow, rather sharply outlined grooves which are somewhat interrupted towards the protoconch, but which are continuous on the outer whorls. Radial sculpture teleoconch: inconspicuous growth lines, next to these inconspicuous to distinct, well-spaced to densely placed, shallow grooves, often at irregular intervals. Umbilicus open, narrow, columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 2.2 mm; width up to 3.6 mm; diameters of the first three whorls 0.4-0.5 mm, 0.8-1.0 mm, 1.2-1.6 mm respectively; number of whorls up to 4 7/8; height aperture up to 1.3 mm; width aperture up to 1.3 mm.

Microcystina gratilla
Habitat in Sabah and distribution. Primary and secondary forest on sandstone bedrock, up to 900 m alt., elsewhere up to 2400 m alt. Sabah: Mount Kinabalu, Mount Tambuyukon; Mount Trusmadi, Crocker Range. Also in Kalimantan. Distribution: Java; Madura, Bali; Flores.
Cross diagnosis. Very similar to M. muscorum, but the sculpture, at least on the protoconch, is different; see below M. muscorum. Juvenile M. appendiculata in which the spur protruding from the columellar corner of the peristome has not yet developed can be distinguished by the absence of well-spaced radial grooves on the teleoconch. Juvenile M. physotrochus has a protoconch with more distinct radial riblets.
Remarks. Most Sabah shells have a comparatively high spire.  Description. Shell very small, thin, slightly translucent, brown; inflated-lenticular to depressed-ovoid; spire (moderately) elevated (more distinctly elevated in some adults) conical with convex sides or depressed-ovoid, with a rounded apex. Surface glossy. Whorls moderately convex. Protoconch: with or without very fine (only just visible at 40 times magnification), well-spaced, somewhat interrupted, shallow, rather sharply outlined spiral grooves; also with patches of fine, densely placed radial riblets, particularly below the suture. Teleoconch: fine, well-spaced, shallow spiral grooves on the upper and lower surface; sometimes only present on part of the shell, or (almost) entirely absent. Radial sculpture teleoconch: inconspicuous growth lines, next to these rather distinct, well-spaced to densely placed shallow grooves, often at irregular intervals. Umbilicus open, narrow; columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 2.3 mm; width up to 2.9 mm; diameters of the first three whorls 0.5-0.7 mm, 0.9-1.2 mm, 1.3-1.8 mm respectively; number of whorls up to 4 7/8; height aperture up to 1.5 mm; width aperture up to 1.6 mm.

Microcystina physotrochus
Habitat in Sabah and distribution. Rainforest, seasonally dry forest, coastal forest, secondary woodland; on limestone and sandstone bedrock, up to 2600 m alt. Sabah: rather common. Usually found in small numbers. Also in Sarawak. Endemic to Borneo.
Cross diagnosis. Generally identified among Sabah Microcystina by the somewhat inflated shell. Relatively flat specimens differ from M. appendiculata because they lack the spur on the columellar side of the peristome.
Elsewhere, the following species have a similar inflated-lenticular or depressedovoid shell of comparable size. Sitala infantilis E.A. Smith, 1895, from Palawan, has a corneous shell with a comparatively larger aperture, and a smooth surface, Microcystina seclusa Godwin Austen, 1891, from Sarawak, has the last whorl more narrowly rounded around the periphery. Lamprocystis ambonica Boettger, 1891, from the Moluccas, has a larger aperture. Sitala amussitata E.A. Smith, 1895, from Sarawak, and Lam-procystis subglobosa Von Moellendorff, 1897 (see Van Benthem Jutting 1950: 452), from Java, have the whorls are slightly laterally compressed, resulting in a somewhat shouldered last whorl.
Philalanka anomphala (see Endodontidae) is characterized by the thinner shell, with much coarser, raised growth lines.
Remarks. Juveniles and some adults have the basal edge of the peristome more angular than in the illustrated specimen. A small callus (not protruding beyond the rim of the peristome, as in M. appendiculata) may be present on the columellar peristome in such shells. Shells from Mount Kinabalu tend to be relatively small, with a distinctly elevated spire.
Habitat and distribution. Tree and rock dwellers. Widespread and species-rich throughout Southeast Asia, Australia, and Oceania.
Remarks. Although the family is well-studied, and some groups have been confidently excluded because of polyphyly, such as the American taxa (Scott 1996;Wade et al. 2007), Solem (1992) refrains from a family diagnosis, as its relation with Bradybaenidae and other members of the helicoid clade remains unclear.
Habitat in Sabah and distribution. Found in shrubby forest on limestone bedrock. Alt. c. 500 m. Sabah: Interor, Pun Batu only. Endemic to Sabah.
Cross diagnosis. The small size, combined with the narrow spire uniquely identifies this species within in the genus Amphidromus.
Etymology. The name refers to the size of the shell [psephos (Gr.) = pebble].
Remarks. The classification of this genus is still unresolved (Solem 1964). We include the species below on account of the similarity of its shell to that of T. pudica Godwin Austen, 1891, a species native to Sabah. With its drawn-out peristome it would also fit in Planispira Beck, 1838, but all species included in this genus have an open umbilicus.
Cross diagnosis. Uniquely identified among Sabah Camaenidae by its beak-like extension of the palatal side of the aperture. The only Sabah species with a similar beak is the ariophantid Rhinocochlis nasuta (Metcalfe, 1851), which has a flat, sharply keeled, entirely white shell without hairs on the periostracum.
Remarks. This species may be endemic to the Sabah areas on ultrabasic bedrock. Etymology. The name refers that the species is found on serpentinite bedrock.

Family ENDODONTIDAE Pilsbry
Short description. Snails. Shell small to medium-sized, dextral, conical, lenticular, or discoidal. Sculpture often rather distinct, consisting of spiral striation and/or radial ribs, sculpture sometimes inconspicuous or absent. Aperture with or without teeth or lamellae, peristome neither thickened nor reflected. Umbilicus closed or open, narrow or wide (Family description adapted from Solem 1976;Schileyko 2001). Habitat and distribution. Generally found in litter and on the vegetation. Worldwide, but particularly species-rich on the islands of and around the Pacific.
Remarks. The status of several genera often included in this family, including the ones we discuss here (Philalanka and Thysanota), has been debated. Raheem et al. (2014) follow Godwin-Austen (1907) in placing these two genera in the Thysanotinae and follow Bouchet and Rocroi (2005) in placing this subfamily in the Charopidae, whereas we have here retained the endodontid placement of Godwin-Austen (1907).
The endodontid genera Philalanka and Thysanota generally include small species with more or less conical shells, and often with one or more distinct spiral threads. Particularly Philalanka displays a wide range of shell shapes, which makes it impossible to find a diagnostic set that unequivocally distinguishes between the genera. However, we feel that including Philalanka, Kaliella and the various satellite genera into a single genus would be unjustified. This is in spite of the fact that we are in favour of genera of convenience, by necessity because in most cases our taxonomy is largely based on shells. The best we can do is to compare groups within Philalanka with groups within Kaliella which share one or two characters.
We provide a review of the Sabah species of the Endodontidae.
Diagnosis for the Sabah species. Shell conical to conical-ovoid, whorls somewhat depressed or not. Teleoconch: Radial sculpture prosocline, indistinct to coarse growth lines only, or with fine growth lines grading into rather densely placed, rather distinct riblets. Last whorl without spiral threads, or with 1-6 distinct spiral threads (next to a number of much finer spiral threads), the lowermost around the periphery, the others above the periphery and often interrupted. Umbilicus open, narrow, or closed. Cross diagnosis. Type of the genus is P. secessa Godwin Austen, from Sri Lanka, a species comparable to P. thienemanni, with a single peripheral thread on the last whorl. Next to these, species with more than one spiral thread (comparable to P. kusana, below) are included by Gude (1914), next to species without any spiral sculpture (comparable to P. malimgunung, below). Species with a single, conspicuous spiral thread and species without a spiral thread are difficult to distinguish from Kaliella (Helicarionidae). Such species have a wider umbilicus than Kaliella. P. anomphala is the exception, with a closed umbilicus, but this has rather coarse, irregularly spaced growth lines, unlike any Kaliella. (1907[1897-1914]: 188), places the genus in the Endodontidae.

Remarks. On account of anatomical characters, Godwin Austen
We divide the genus into two informal groups.
Group 1. Last whorl with 2 or more distinct spiral threads (rare specimens of P. tambunanensis and P. kusana have 1 spiral thread).  Description. Shell very small, thin, translucent to opaque, pale brown-or yellowcorneous to white, conical with flat or slightly convex sides; apex widely rounded. Surface with a silky luster. Whorls convex, rounded. Protoconch whorls convex; sculpture: 10-15 rather distinct, thin spiral threads; radial sculpture approx. absent or some very fine, subordinate wrinkles. Teleoconch: Last whorl with (1-)2 inconspicuous to distinct, narrow spiral threads (1 above the periphery, sometimes absent; 1 below the periphery, coinciding with the suture of the penultimate whorl); next to these a distinct, fine, rather dense spiral striation present, sometimes less conspicuous just below the suture; below the lowermost spiral thread the spiral striation is (somewhat) more widely spaced and gradually disappears towards the umbilicus. Radial sculpture most distinct below the suture: fine growth lines grading into rather densely placed, rather distinct riblets; the interstices between these riblets cut into the crests of the spiral striation. Umbilicus open, rather narrow. Dimensions: Height up to 2.3 mm; width up to 2.5 mm; diameters of the first four whorls 0.55-0.80 mm, 0.95-1.20 mm, 1.45-1.80 mm, 2.0-2.3 mm respectively; number of whorls up to 5; height aperture up to 1.0 mm; width aperture up to 1.3 mm.

Philalanka tambunanensis
Habitat in Sabah and distribution. Damp primary forest around streams, on limestone and sandstone bedrock, 500-1000 m alt. Sabah: Upper Padas River, Tam bunan valley. Endemic to Sabah.
Cross diagnosis. Differs from P. kusana by the more distinct spiral striation next to the two threads, as well as a more distinct radial sculpture. As a result, the shell is not shiny, but has a silky luster. Philalanka tambunanensis usually has two spiral threads; P. kusana usually has three, sometimes two. Philalanka carinifera (Stoliczka), from Peninsular Malaysia, is more densely coiled (diameters of the first four whorls 0.4-0.5 mm, 0.70-0.85 mm, 1.05-1.20 mm, 1.4-1.6 mm respectively), and has a shiny surface with inconspicuous sculpture only, apart from the spiral threads.
Etymology. The name refers to the area where the species is found. Figure 43 Trochomorpha kusana    Description. Shell very small, thin, translucent to opaque, light brown to pale yellow-corneous to white, conical with slightly convex sides, sometimes conicalovoid; apex rounded. Surface shiny. Whorls convex, rounded or slightly angular because of the presence of strong spiral threads, somewhat flattened below the lowermost spiral thread, sometimes somewhat flattened above the upper spiral thread. Protoconch whorls convex; sculpture: (1-)4-6(-9) inconspicuous to distinct, thin spiral threads; radial sculpture absent or some subordinate wrinkles. Teleoconch: Last whorl with (2-)3(-4) distinct, narrow spiral threads (when 2: 1 above and 1 below the periphery; when 3-4: 1 at the periphery, 1 well below, and 1-2 above), the lowermost coinciding with the suture of the penultimate whorl; between the spiral threads often (traces of) a fine, rather dense to moderately spaced spiral striation; below the lowermost spiral thread a similar moderately to widely spaced spiral striation which gradually disappears towards the umbilicus. Radial sculpture most distinct below the suture: fine growth lines, locally grading into somewhat spaced riblets. Umbilicus open, narrow. Dimensions: Height up to 3.2 mm; width up to 3.5 mm; diameters of the first four whorls 0.6-0.8 mm, 1.0-1.3 mm, 1.6-2.0 mm, 2.1-2.7 mm respectively; number of whorls up to 5 1/2; height aperture up to 1.1 mm; width aperture up to 1.6 mm.
Cross diagnosis. Philalanka tjibodasensis (Leschke), from Java, has a comparable size and mode of coiling (diameter of the first four whorls c. 0.6 mm, 1.1 mm, 1.6 mm, 2.4 mm respectively). It differs by having flattened protoconch whorls without spiral sculpture.
Remarks. Most individuals of P. kusana have 3 spiral threads, but large samples usually include a small number of specimens with only 2 spiral threads. In a few samples from the Crocker Range, Kappes (unpublished report) suspects two discrete species within our concept of P. kusana, based on molecular data and supported by slight differences in protoconch sculpture. We find a wide variability in protoconch sculpture, and cannot accordingly divide all material available.
Aldrich (1889) describes the shell colour as light brown. All specimens seen by us range from pale yellow-corneous to white.    Description. Shell very small, rather thin, more or less opaque, brown, very rarely yellowish, conical with approx. flat or slightly convex sides; apex rounded. Surface about dull or with a silky luster above the periphery, glossy below. Whorls convex, approx. rounded. Protoconch whorls convex; sculpture: 9-12 inconspicuous to distinct, very fine, thin spiral threads; radial sculpture absent or some subordinate wrinkles. Teleoconch: Last whorl with a distinct spiral thread coinciding with the suture of the penultimate whorl, above this 2-4 slightly less distinct threads with a very fine (just visible at 40 times magnification) spiral striation in between, particularly towards the periphery; below the periphery up to 4 fine spiral threads close to it, with very fine spiral striation in between. Radial sculpture: densely placed, very fine (just visible at 40 times magnification), narrow riblets that may be inconspicuous locally. Umbilicus open, narrow. Dimensions: Height up to 2.9 mm; width up to 2.8 mm; diameters of the first four whorls 0.55-0.65 mm, 0.9-1.1 mm, 1.35-1.55 mm, 1.9-2.1 mm respectively; number of whorls up to 5 7/8; height aperture up to 1.2 mm; width aperture up to 1.6 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone and sandstone soil, up to 1100 m alt. Sabah: West part; scattered localities along East coast. Also in Sarawak. Endemic to Borneo.
Cross diagnosis. Resembles Kaliella microconus (Mousson), which also occurs in Sabah, but it has much coarser and less regularly spaced spiral threads, and more convex whorls.  Description. Shell very small, rather thin, more or less opaque, (dark) brown, sometimes yellowish, conical with approx. flat or slightly convex sides; apex rounded. Surface about dull or with a silky luster above the periphery, glossy below. Whorls convex, approx. rounded. Protoconch whorls convex; sculpture: 9-12 inconspicuous to distinct, very fine, thin spiral threads; radial sculpture absent or some subordinate wrinkles. Teleoconch: Last whorl with a distinct spiral thread coinciding with the suture of the penultimate whorl, above this 3-4 about equally distinct threads, and in between up to 2 less distinct ones; below the lowermost thread a very fine spiral striation close to it, sometimes with up to 4 slightly coarser threads interspersed. Radial sculpture: densely placed, very fine (just visible at 40 times magnification), narrow riblets that may be inconspicuous locally. Umbilicus open, narrow. Dimensions: Height up to 2.7 mm; width up to 2.4 mm; diameters of the first four whorls 0.5-0.65 mm, 0.85-1.00 mm, 1.15-1.35 mm, 1.5-1.8 mm respectively; number of whorls up to 5 3/4; height aperture up to 0.9 mm; width aperture up to 1.3 mm.

Philalanka obscura
Habitat in Sabah and distribution. Primary and secondary forest on limestone and sandstone soil, up to 500 m alt. Sabah: scattered localities. Also in Kalimantan. Endemic to Borneo.
Cross diagnosis. Differs from P. moluensis by not having a fine spiral striation in between the spiral threads above the periphery, except for a few subordinate threads. Next to this, the shells are usually higher conical, and the spiral threads are thicker.
Etymology. The name refers to the shell colour [obscurus (L.) = dark]. Description. Shell very small, very thin, translucent, pale yellow-corneous to white, conical with convex sides, to almost conical-ovoid; apex rounded. Surface glossy. Whorls moderately convex, last whorl rounded or slightly angular because of the presence of a strong spiral thread. Protoconch whorls convex, smooth or with 1-6 very inconspicuous, thin spiral threads. Teleoconch: last whorl with a distinct, thick peripheral thread coinciding with the suture of the penultimate whorl; next to this thread (traces of) very fine, inconspicuous, well-spaced, very thin spiral threads present except in the umbilical region; with or without (traces of) an even finer (just visible at 40 times magnification), dense spiral striation in between these threads, especially above the peripheral thread. Radial sculpture: locally a few inconspicuous, well-spaced growth lines, locally also very fine (barely visible at 40 times magnification), densely placed riblets. Umbilicus open, wide. Dimensions: Height up to 2.35 mm; width up to 2.6 mm; diameters of the first four whorls 0.5-0.6 mm, 0.90-1.05 mm, 1.3-1.6 mm, 1.80-2.15 mm respectively; number of whorls 6; height aperture up to 0.8 mm; width aperture up to 1 mm.

Group 2. Last whorl with 1 spiral thread, or without a spiral thread
Habitat in Sabah and distribution. Found in damp forest on sandstone soil, at 500-1700 m alt. Sabah: Crocker Range. Distribution: Thailand; Java; Bali; Flores.
Remarks. Shells from Thailand (V5603, from Chiang Mai) have a slightly more distinct spiral sculpture, particularly on the lower surface, than shells from Java. The Borneo shells are intermediate in this respect.  Description. Shell very small, thin, hardly translucent, yellow-corneous, low-conical with slightly convex sides; apex somewhat flattened. Surface glossy. Whorls convex, rounded. Protoconch whorls convex; surface almost smooth, the slightest traces of a very fine (just visible at 40 times magnification), dense spiral striation, as well as some traces of radial sculpture. Teleoconch: Last whorl with a thin, inconspicuous (conspicuous in juveniles) spiral thread following the periphery and coinciding with the suture of the penultimate whorl; above this traces of very fine (just visible at 40 times magnification), rather dense spiral striation, below the periphery with a similar, but widely spaced, striation; this spiral striation subordinate to rather coarse, moderately spaced but irregularly placed, usually somewhat sunk growth lines above the periphery, radial sculpture below the periphery less conspicuous. Umbilicus closed, rimate in juveniles.

Philalanka rugulosa Vermeulen, Liew & Schilthuizen, sp. n.
http://zoobank.org/3878A617-9773-4C10-8B88-0A4084027838 Figure 48 Holotype. Malaysia Description. Shell very small, very thin, hardly translucent, yellowish brown, (low) conical with slightly convex sides; apex rounded. Surface with a silky luster. Whorls convex above and below the periphery, periphery rounded to slightly angular (in adults, more distinctly angular in juveniles, suture somewhat impressed. Protoconch whorls moderately convex; almost smooth with the slightest traces of a radial sculpture, and a very fine, dense spiral striation. Teleoconch: last whorl sometimes with a thin, inconspicuous peripheral thread coinciding with the suture of the penultimate whorl; some traces of a fine, dense spiral striation below this thread. Radial sculpture: rather distinct, irregularly spaced, somewhat raised growth lines, grading into more regularly and rather densely placed, low riblets; towards the umbilicus the growth lines tend to become less conspicuous. Umbilicus open, narrow. Dimensions: Height up to 2.7 mm; width up to 3.4 mm; diameters of the first three whorls 0.65-0.75 mm, 1.2-1.4 mm, 2.25-2.60 mm respectively; number of whorls up to c. 4 1/4; height aperture up to 1.5 mm; width aperture up to 1.75 mm. Habitat in Sabah and distribution. Subalpine vegetation on granodiorite soil. Alt. 2900-4100 m. Sabah: Mount Kinabalu (summit trail area). Endemic to Sabah.
Cross diagnosis. Distinctly larger than P. anomphala and P. malimgunung; from the first it also differs by having an umbilicate shell.
Philalanka lieftincki Van Benthem Jutting, 1953 (Indonesia, Ambon) looks similar but is smaller (shell 1.5-1.9 mm high, at 4-4 1/2 whorls). Philalanka micromphala Van Benthem Jutting, 1952 (Indonesia, Java) is of similar shape and size, but has a more angular last whorl with a distinct peripheral thread, a finer radial sculpture and a more depressed aperture (aperture 1.1-1.2 mm high, at a shell height of 2.1-2.7 mm).
Kaliella scandens and K. doliolum are similar in shape but have a far more regular radial sculpture, consisting of densely placed ribs.

Philalanka malimgunung Vermeulen, Liew & Schilthuizen, sp. n.
http://zoobank.org/33E06180-04E1-4A2B-8C80-41DB4216F799 Figure 49 Holotype. Malaysia Description. Shell minute, very thin, hardly translucent, pale yellow-brown, yellow-corneous below, (low-)conical with approx. flat sides; apex rounded. Surface with a silky luster. Whorls convex, rounded (angular in juveniles), suture somewhat impressed. Protoconch whorls moderately convex; with inconspicuous, very fine (just visible at 40 times magnification) and dense spiral striation. Teleoconch with very fine (just visible at 40 times magnification), dense spiral striation above the periphery, which is continuous on the top whorls but more patchy on the last whorl; with a similar but somewhat more widely spaced striation below the periphery; spiral striation somewhat subordinate to the rather distinct, irregularly spaced, slightly raised growth lines, which are less conspicuous towards the umbilicus. Umbilicus open, rather narrow. Dimensions: Height up to 1.4 mm; width up to 1.9 mm; diameters of the first three whorls 0.45-0.50 mm, 0.85-1.00 mm, 1.40-1.55 mm respectively; number of whorls up to c. 3 1/2; height aperture up to 0.8 mm; width aperture up to 0.9 mm.
Cross diagnosis. Most similar in size and shape to P. anomphala, it differs by having an open umbilicus, and by lacking the peripheral thread. It also differs from the extralimital species listed under P. rugulosa by the lack of a peripheral thread.
Etymology. The species is named in recognition of generations of mountain guides ('Malim Gunung') who assist tourists and scientists on their way to the peaks of Mount Kinabalu every day, and who have aided scientific discoveries on this mountain since the first documented exploration of Mount Kinabalu in 1851. The species name also serves to honour the guides who lost their lives protecting mountain climbers when Mount Kinabalu was struck by earthquake on June 5 th , 2015.
Diagnosis for the Sabah species. Shell conical, with almost flat sides, with depressed whorls. Teleoconch: Radial sculpture prosocline, consisting of densely placed to moderately spaced, fine riblets. Last whorl with 2-3 distinct spiral threads (next to a number of much finer spiral threads), the lowermost around the periphery, the others above the periphery and often interrupted. Umbilicus open, narrow, or closed.
Cross diagnosis. The Sabah species of Thysanota differ from Philalanka by the combination of a conical spire, with almost flat sides, somewhat depressed whorls and a very narrow, or closed umbilicus.
Remarks. The generic position of the two species listed below is unresolved. Solem (1988: 552) places T. grenvillei in the Helicarionidae, although he finds its anatomy different from other Australian helicarionid genera. Godwin Austen (1907Austen ( [1897Austen ( -1914: 189) dissects an Indian species, T. carinigera (Benson), and places the genus in the Endodontidae. Solem also expresses the possibility that T. conula (as Liardetia fimbriosa), and T. grenvillei belong to the same genus. With several more samples of both species at hand from widely scattered localities in S. and S.E. Asia, we conclude that their shells, at least, show striking similarity. The genus Thysanota includes more species with similar shells (see Gude 1914: 10;Naggs and Raheem 1999: 23); we feel that the species below are best placed in this genus. Figure 50 Nanina conula Blanford, 1865: 73 Description. Shell very small, rather thin, somewhat translucent or opaque, pale brown to white, high-conical with approx. flat sides; apex rounded. Surface about dull or with a silky luster above the periphery, shiny below. Whorls moderately convex, (moderately) angular at the periphery, above the periphery slightly rounded or almost flat, below the periphery with a second, moderate angle at a distance from the periphery, below this almost flat. Protoconch whorls convex, with 10-15 distinct, fine, rather densely placed, thin spiral threads; radial sculpture absent or subordinate. Teleoconch: Last whorl with a distinct peripheral spiral thread, below the periphery with a second, equally distinct spiral thread at a distance from the periphery, and coinciding with the suture of the penultimate whorl; next to these two with numerous much finer,  (Blanford, 1865). Frontal view, shell 1.5 mm high (Indonesia, Nusa Penida, Tengasa, V 4086) 51 Thysanota grenvillei (Brazier, 1876 well-spaced spiral threads, which become finer and more widely spaced towards the suture and towards the umbilicus. Radial sculpture: growth lines above the periphery and particularly below the suture grading into rather densely placed to moderately spaced, fine, narrow riblets at more or less regular distances. which may form slight nodes where they cross the spiral threads. Umbilicus closed, or open, narrow. Dimensions: Height up to 2.3 mm; width up to 1.6 mm; diameters of the first four whorls 0.40-0.45 mm, 0.60-0.65 mm, 0.80-0.95 mm, 1.05-1.30 mm respectively; number of whorls up to 6 1/2; height aperture up to 0.5 mm; width aperture up to 0.9 mm.

Thysanota conula (Blanford, 1865)
Habitat in Sabah and distribution. Found near a limestone cliff in logged forest, at 400-500 m alt. Elsewhere in a range of disturbed environments, drought tolerant. Sabah: Interior, Sepulut valley. Distribution elsewhere: India; Vietnam; Peninsular Malaysia; Southwards to Java; Eastwards to Halmahera.
Remarks. The relative width of the shell shows some variability: some shells are slightly higher than wide, others are distinctly higher than wide. Figure 51 Helix grenvillei  Description. Shell very small, rather thin, somewhat translucent or opaque, (pale) brown, somewhat depressed conical with approx. flat sides; apex rounded. Surface about dull or with a silky luster above the periphery, shiny below. Whorls moderately convex, (moderately) angular at the periphery, above the periphery rounded or with a second, slight angle at a distance from the periphery, below the periphery rounded. Protoconch whorls convex, with 7-10 rather distinct, very fine, well-spaced, thin spiral threads; radial sculpture absent. Teleoconch: Last whorl with a distinct peripheral spiral thread coinciding with the suture of the penultimate whorl, above this 1(-2) less distinct threads as well as numerous very fine spiral threads, the latter more widely spaced towards the upper suture; below the peripheral thread a number of finer threads close to it, as well as a fine, continuous, moderately spaced striation over most of the lower surface. Radial sculpture: growth lines, above the periphery grading into densely placed, rather regularly spaced, fine, narrow riblets, which form minute nodes where they cross the spiral threads. Cross diagnosis. More depressed conical than T. conula, with the shell wider than high. Remarks. The Borneo material is virtually identical with the Australian shell shown in Solem (1988: 552), and with material collected by the first author in Ha Long Bay, northern Vietnam. Australian shells have periostracal hairs where the more distinct spiral threads cross the radial ribs. In some Vietnam shells these hairs are fused to low, erose periostracal crests on the spiral threads. In the Borneo shells, all periostracum has worn off.

Thysanota grenvillei (Brazier, 1876)
The species is now known from three widely distant coastal areas. It is probably a widespread element of the coastal fauna, but appears very rare. It is not an Australian endemic species, as was assumed so far.

Family EUCONULIDAE Baker
Short description. Snails. Shell (very) small, dextral, conical, ovoid or sometimes lenticular. Sculpture inconspicuous, consisting of very fine spiral striation and/or radial riblets. Aperture without teeth or lamellae, peristome neither thickened nor reflected. Umbilicus closed, or covered by a thin callus extending from the peristome, or open, narrow (Family description adapted from Baker 1941, Solem 1966.
Habitat and distribution. Generally dwelling in litter and low vegetation. Worldwide.
Diagnosis for the Sabah species. Teleoconch: Radial sculpture prosocline, consisting of fine growth lines or densely placed to moderately spaced, fine riblets. Last whorl without prominent spiral threads (numerous very fine spiral threads may be present), or with 1 spiral thread or keel at the periphery.
Remarks. The inclusion of the species listed below in Kaliella is merely a convenience, as is the inclusion of our concept of Kaliella in the Euconulidae. Both are inspired by an overall similarity of the shells. It is certain that our arrangement does not reflect phylogenetic relationships between the species. In fact, anatomical analysis of 5 Sabah species (Tillier and Bouchet 1988) reveals major differences between them, and consequently they are accommodated in two new genera Gunongia and Kionghutania. These genera are characterized by properties of the shell, radula and anatomy. We prefer not to apply the four generic names mentioned. Approximately half of the species listed below are only known by their shells, and we cannot unequivocally extend the division into four different genera over all the Sabah species. Until more phylogenetic details become apparent, we prefer to re-instate the old genus Kaliella. The genus Kaliella is typified by a species occurring in Sabah: K. barrakporensis (Pfeiffer).
We provide a review of the Sabah species of Kaliella. We divide the genus into four informal groups.    Description. Shell very small, thin, somewhat translucent, pale brown, conical with flat sides; apex rounded. Surface shiny. Top whorls moderately convex, outer whorls slightly convex, last whorl angular at the periphery, slightly convex below the periphery. Protoconch whorls convex, with predominant, well-spaced, very thin spiral threads, and very fine, densely and somewhat irregularly placed radial riblets. Teleoconch: Spiral sculpture predominant, above the periphery with fine, well-spaced, very thin spiral threads (usually 10 or fewer on the last whorl); below the periphery and close to it with a few to many more of such threads, towards the umbilicus sometimes with much finer, densely placed grooves. Radial sculpture teleoconch: above the periphery growth lines grading into very fine, densely and somewhat irregularly placed radial riblets; below the periphery with irregularly spaced growth lines only. Umbilicus open, very narrow. Dimensions: Height up to 3.0 mm; width up to 2.9 mm; diameters of the first four whorls 0.45-0.60 mm, 0.75-1.00 mm, 1.05-1.45 mm, 1.45-2.00 mm respectively; number of whorls up to 6 1/8; height aperture up to 0.9 mm; width aperture up to 1.4 mm. Radula: central 3-cuspid; laterals and marginals similar, serrate with 2 large cones at the tip.
Habitat in Sabah and distribution. Primary and secondary forest on limestone and sandstone soil. Alt. up to 1000 m, elsewhere up to 1700 m alt. Sabah: wide spread. Also in Sarawak; Kalimantan. Distribution elsewhere: Vietnam; Peninsular Malaysia to Java; Eastwards to Australia; Fiji; Samoa.
Remarks. Information on the radula is from Van Benthem Jutting (1950). No Sabah material included in K. microconus has been checked for radula characters. Figure 55 Kionghutania humilis Tillier & Bouchet, 1988: 275 Description. Shell very small, thin, about opaque, greenish brown, (low) conical with flat or slightly convex sides; apex rounded. Surface shiny. Top whorls moderately convex, outer whorls moderately convex and somewhat shouldered, last whorl angular at the periphery, slightly convex below the periphery. Protoconch whorls convex, with predominant, very fine, well-spaced, thin spiral threads, radial sculpture inconspicuous. Teleoconch: Spiral sculpture predominant, above the periphery with fine, very densely placed, somewhat irregularly spaced, thin spiral threads (30 or more on the fifth whorl); below the periphery with very fine, widely spaced threads, with or without numerous still finer, densely placed grooves in between. Radial sculpture teleoconch: above the periphery with raised growth lines at irregular intervals, most distinctly so just below the periphery; below the periphery the growth lines are less distinct. Umbilicus open, narrow. Dimensions: Height up to 3.3 mm; width up to 4.1 mm; diameters of the first four whorls 0.6-0.7 mm, 1.05-1.15 mm, 1.6-1.7 mm, 2.35-2.50 mm respectively; number of whorls up to 5 7/8; height aperture up to 1.4 mm; width aperture up to 2 mm. Radula: central 3-cuspid; laterals 3-cuspid; marginals serrate with 2 large cones at the tip.
Cross diagnosis: Shares the distinct sculpture of spiral threads above and below the periphery with K. microconus, but differs by the wider shell with more convex, slightly shouldered whorls, and the much more numerous and more densely placed spiral threads. The sympatric K. kinabaluensis and K. nephelophila differ unequivocally by the slightly more concave outline of the spire, whorls without a shoulder, and by the absence of spiral threads on the lower surface (a fine sculpture of spiral grooves may be present).
Habitat in Sabah and distribution. Upper montane forest on granodiorite soil. Alt. 3000-3100 m. Sabah: Mount Kinabalu (summit trail area). Endemic to Sabah.

Cross diagnosis.
Kaliella nephelophila is similar to K. kinabaluensis. Diagnostic is the spiral sculpture above the periphery: fine but still distinct spiral threads, particularly towards the periphery, in K. nephelophila; an indistinct, dense spiral striation in K. kinabaluensis. The two species differ anatomically; see Tillier and Bouchet 1988. Figure 57 Kionghutania kinabaluensis Tillier & Bouchet, 1988: 271 Description. Shell small, very thin, somewhat translucent, slightly greenish brown, conical with flat or slightly concave sides; apex rounded. Surface shiny. Whorls moderately convex and not shouldered, last whorl angular at the periphery, moderately convex below the periphery. Protoconch whorls somewhat convex, with spiral sculpture predominant but inconspicuous, very fine, well-spaced, thin threads; radial sculpture inconspicuous. Teleoconch: subordinate spiral striation, first whorls with traces of very inconspicuous, moderately-spaced striation, outer whorls above the periphery with a very fine, very densely placed, somewhat wavy striation (more than 100 striae on the last whorl); below the periphery almost smooth, with faint traces of an even finer spiral striation only towards the periphery. Radial sculpture teleoconch: Above the periphery with coarse, distinctly raised growth lines at irregular intervals; below the periphery these are slightly less distinct. Umbilicus closed. Dimensions: Height up to 5.6 mm; width up to 6.2 mm; diameters of the first four whorls 0.8-0.85 mm, 1.2-1.3 mm, 1.80-1.95 mm, c. 2.7 mm respectively; number of whorls up to 6 1/8; height aperture up to 2.4 mm; width aperture up to 3.2 mm. Radula: central 3-cuspid; laterals 3-cuspid; marginals serrate with 2 large cones at the tip.
Cross diagnosis. Very similar to K. nephelophila; see note under the latter. Figure 58, 63

Kaliella dendrophila (Van Benthem Jutting, 1950)
Liardetia dendrophila Van Benthem Jutting, 1950: 407;Clements et al. 2008Clements et al. : 2762Schilthuizen et al. 2013 Description. Shell very small, thin, translucent, very pale greenish to yellowish, somewhat depressed-conical with flat sides; apex rounded. Surface shiny. Whorls: Top whorls convex, outer whorls (almost) flat, last whorl sharply angular at the periphery, almost flat or slightly convex above and below. Protoconch whorls convex, with distinct, moderately spaced, rounded spiral threads, radial sculpture absent or inconspicuous, subordinate. Teleoconch: A slight, obtuse keel present around the periphery; above and below with rather distinct, well-spaced (particularly half-way between suture and periphery, as well as just below the periphery) spiral threads, which consist of rows of densely placed beads which are often elongated in the direction of the growth lines. Radial sculpture: above the periphery with some rather distinct, irregularly spaced, somewhat raised growth lines, next to these locally some very fine, inconspicuous, moderately spaced, low and thin riblets; below the periphery with a few inconspicuous, irregularly spaced growth lines only. Umbilicus open, very narrow, or closed. Dimensions: Height up to 2.7 mm; width up to 4.1 mm; diameters of the first four whorls 0.55-0.67 mm, 1.1-1. 5 mm, 2.1-2.7 mm, c. 3.6 mm respectively; number of whorls up to 4 1/2; height aperture up to 1.6 mm; width aperture up to 2 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone soil. Alt. 0-500 m. Sabah: Crocker Range; Kinabatangan River valley.
River valley. Distribution elsewhere: Peninsular Malaysia; Java; Sulawesi; Ambon. Cross diagnosis. Easily recognizable within group 1 by the spiral sculpture on the teleoconch, above the periphery. K. punctata, of group 2, has a similar spiral sculpture, but consisting of pits. It also has a higher conical shell with whorls that increase much less rapidly in width. K. gregaria and K. microsoma have a similar shell but a spiral sculpture not consisting of rows of beads.
Remarks. Van Benthem Jutting (1950: 407) describes the spiral striation as engraved into the shell surface. SEM images show that it consists of interrupted spiral threads.
Group 2. Protoconch with fine spiral grooves, usually about as strong as the radial sculpture or weaker, or protoconch without spiral sculpture.
Group 2a. Diameter of the third whorl more than 2.3 mm (also check K. punctata and K. calculosa, with incidental shells having a third whorl of 2.2 mm diameter). Figure 59 Gunongia gregaria Tillier & Bouchet, 1988: 264 Description. Shell small, very thin, somewhat translucent, greenish or brownish, depressed-conical with flat sides; apex rounded. Surface shiny. Whorls moderately convex, last whorl angular and slightly compressed at the periphery, rounded above and below the periphery. Protoconch whorls convex, with numerous fine, rather densely placed radial riblets; spiral sculpture subordinate and inconspicuous (visible at 40 times magnification), numerous very densely placed grooves. Teleoconch: Last whorl with a peripheral spiral thread coinciding with the suture of the penultimate whorl, above and below this numerous continuous, fine, densely and regularly placed spiral grooves. Radial sculpture: above the periphery rather distinct, irregularly spaced, somewhat raised growth lines, next to these fine, densely and regularly placed (about as densely as the spiral grooves) riblets; below the periphery with similar but less distinct radial sculpture.  Description. Shell small, rather thin, somewhat translucent or opaque, pale yellowcorneous to white, depressed-conical with approx. flat or slightly convex sides; apex rounded. Surface shiny. Whorls moderately convex, last whorl angular at the periphery, rounded above and below the periphery. Protoconch whorls convex, with numerous fine, rather densely placed radial riblets, which are most distinct below the suture; numerous approx. equally strong, densely placed spiral grooves cutting into the crests of the radial riblets. Teleoconch: Last whorl with a peripheral spiral thread coinciding with the suture of the penultimate whorl, above and below this numerous fine, moderately and regularly spaced, continuous spiral grooves. Radial sculpture: growth lines above the periphery, at somewhat irregular intervals, which are approx. as strong as the spiral sculpture, and which are most distinct just below the suture. Umbilicus closed. Dimen- Figure 59. Kaliella gregaria (Tillier & Bouchet, 1988). A Frontal view B Umbilical view C Apical view (Malaysia, Sabah, Kinabalu N.P., V 14329, aperture reconstructed). sions: Height up to 2.65 mm; width up to 3.8 mm; diameters of the first four whorls 0.80-0.85 mm, 1.5-1.6 mm, 2.35-2.50 mm, 3.6-3.7 mm respectively; number of whorls up to 4 1/8; height aperture up to 1.5 mm; width aperture up to 2.0 mm.
Cross diagnosis. Differs from K. gregaria by its smaller size, at the same number of whorls. In K. eurytrochus, the whorls increase less fast in width; compare the diameters of the third whorl of both species. The shell of K. eurytrochus is also distinctly thicker, and less fragile.
Etymology. The name refers to the inflated shell shape [eurus (Gr.) = wide; trokhos (Gr.) = wheel, a word often used for the gastropod spire].

Kaliella sublaxa Vermeulen, Liew & Schilthuizen, sp. n.
http://zoobank.org/CE4B221C-E4DD-4324-8AFB-8F305C6A7196 Figure 61 Holotype. Malaysia, Sabah, West Coast Province, Crocker Range N.P., km 54 marker on the road Kota Kinabalu-Tambunan, Gunung Mas (RMNH.5003923).  Description. Shell small, very thin, somewhat translucent, pale yellowish-brown, somewhat depressed-conical with flat or slightly concave sides; apex rounded. Surface shiny. Whorls moderately convex, last whorl slightly angular, rounded above and below the periphery. Protoconch whorls rather flat, with numerous fine, densely placed radial riblets; spiral sculpture virtually absent. Teleoconch: Last whorl with a thin peripheral spiral thread coinciding with the suture of the penultimate whorl, above and below this numerous fine, densely and regularly placed, continuous spiral grooves. Radial sculpture: above the periphery with a few growth lines, next to these fine, densely and regularly placed (about as dense and as strong as the spiral grooves) riblets; below the periphery with similar but less distinct radial sculpture. Umbilicus closed. Dimensions: Height up to 3.5 mm; width up to 4.1 mm; diameters of the first four whorls 0.7-0.8 mm, 1.35-1. 50 mm, 2.40-2.65 mm, c. 3.9 mm respectively; number of whorls up to c. 4; height aperture up to 2.2 mm; width aperture up to 2.4 mm. Habitat in Sabah and distribution. Primary and secondary forest on limestone and sandstone soil. Alt. 900-1700 m. Sabah: Crocker Range; Gunung Trusmadi. Endemic to Sabah.
Cross diagnosis. In general shape most similar to K. dendrophila, differs by the protoconch sculpture with predominant radial riblets and the more convex outer whorls. Also similar to K. calculosa and K. microsoma, differs by the less dense mode of coiling (compare the width of the third and fourth whorl).
It differs from K. gregaria by its denser mode of coiling (compare diameters of the third whorl), and from K. eurytrochus by the more dense spiral sculpture on the outer whorls, above the periphery, as well as by the larger aperture at the same number of whorls.
Etymology. The name refers to the mode of coiling [sub-laxa (L.) = a little loose].
Group 2b. Periphery of last whorl angular in adult shells, or with a peripheral spiral thread. Diameter of the third whorl 2.2 mm or less. Spiral sculpture teleoconch fine but distinct above the periphery.  Description. Shell very small, rather thin, somewhat translucent or opaque, yellow-brown corneous, depressed-conical to almost lenticular with slightly convex sides; apex rounded. Surface shiny. Whorls moderately convex, the last whorl angular at the periphery, rounded above and below the periphery. Protoconch whorls convex, with numerous fine, densely placed radial riblets; spiral sculpture subordinate, consisting of approx. 12 very fine, densely placed spiral grooves cutting into the crests of the radial riblets. Teleoconch: Last whorl with a peripheral spiral thread coinciding with the suture of the penultimate whorl, above and below this numerous continuous, fine, moderately and regularly spaced, continuous spiral grooves. Radial sculpture: growth lines above the periphery only. Umbilicus open, narrow. Dimensions: Height up to 1.7 mm; width up to 2.6 mm; diameters of the first four whorls 0.55-0.65 mm, 0.95-1.10 mm, 1.45-1.60 mm, 2.05-2.30 mm respectively; number of whorls up to 4 3/4; height aperture up to 1.05 mm; width aperture up to 1.3 mm.
Cross diagnosis. Uniquely identified among Sabah Kaliella species by its depressed-conical, almost lenticular spire.
Habitat in Sabah and distribution. Primary and secondary forest on limestone and granodiorite soil, up to 1700 m alt. Sabah: Mount Kinabalu; Interior; East coast. Also in Sarawak; Kalimantan. Distribution elsewhere: Sulawesi.
Cross diagnosis. Uniquely identified by the pitted spiral sculpture on the teleoconch, in combination with its size. In Kaliella dendrophila, of group 1, the spiral sculpture consist of beads on the shell surface, not pits in the shell surface. It is much smaller, has a thinner, more translucent shell with a smaller protoconch with predominant spiral sculpture, and with whorls more rapidly increasing in size.
Remarks. The spiral sculpture above the periphery is fine in some specimens, somewhat coarser in others. The continuous spiral striation below the periphery is absent in some specimens.
Etymology  Description. Shell small, very thin, translucent, pale yellowish-green to pale yellowish-brown, conical with about flat sides. Surface with a silky luster, shiny below the periphery. Whorls somewhat convex, last whorl almost rounded to angular at the periphery, moderately convex below the periphery. Protoconch sculpture: distinct, fine, densely placed radial riblets; spiral sculpture slightly subordinate, equally densely placed or slightly wider spaced grooves cutting into the crests of the radial riblets. Teleoconch: Last whorl with or without a thin peripheral spiral thread coinciding with the suture of the penultimate whorl, above and below this with very fine to rather coarse, moderately to widely spaced, continuous, sometimes rather shallow and wide grooves cutting through the radial riblets. Radial sculpture teleoconch subordinate: above the periphery inconspicuous growth lines, next to these very fine, densely and regularly placed riblets, sometimes on the outer whorls locally interrupted by approximately smooth areas; below the periphery with occasional growth lines only. Umbilicus open, very narrow. Dimensions: Height up to 5.0 mm; width up to 4.6 mm; diameters of the first four whorls 0.65-0.75 mm, 1.15-1.25 mm, 1.75-2.10 mm, 2.6-3.2 mm respectively; number of whorls up to c. 5 3/4; height aperture up to 2.5 mm; width aperture up to 2.7 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone and sandstone soil. Alt. up to 1000 m. Sabah: Crocker Range; Interior; East coast; scattered localities. Distribution elsewhere: From India, Laos, to Australia; Eastwards to Tahiti.
Cross diagnosis. When fresh, shell thinner and more translucent than the other species in this group, K. dendrophila excepted. Juveniles can be distinguished from that species by the different apical sculpture.
Elsewhere, Kaliella sitaliformis Von Moellendorff 1897, from Java, Bali, and Sulawesi, differs by having a raised spiral sculpture, visible in between the radial riblets, on the outer whorls.
Remarks. K. calculosa shows considerable variability in the prominence and the density of the spiral sculpture on the teleoconch. SEM-images show that the widest spiral grooves have a distinctly convex bottom; it is as if a thin thread is embedded in the groove.  Description. Shell very small, very thin, somewhat translucent, greenish-brown, conical with slightly convex sides; apex rounded. Surface with a silky luster. Top whorls convex, outer whorls only a little less convex, last whorl angular at the periphery, somewhat obtusely so near the aperture in adult specimens, moderately convex below the periphery. Protoconch whorls convex, with very fine, densely placed radial riblets; spiral sculpture subordinate and sometimes inconspicous, very densely placed grooves, just visible at 40 times magnification. Teleoconch: Last whorl with a peripheral spiral thread coinciding with the suture of the penultimate whorl, above the periphery fine, moderately spaced, narrow spiral grooves that cut into the crests of the radial riblets and that are slightly to distinctly subordinate to these; below the periphery with similar, but slightly more distinct and slightly more spaced grooves. All spiral sculpture varies from rather distinct to inconspicuous and only locally present. Radial sculpture teleoconch: above the periphery rather inconspicuous, irregularly spaced, somewhat raised growth lines, next to these fine, very densely and regularly placed riblets on the inner whorls, less densely placed riblets locally present on the outer whorls; radial sculpture less conspicuous below the periphery. Umbilicus closed. Dimensions: Height up to 1.6 mm; width up to 1.8 mm; diameters of the first three whorls 0.45-0.55 mm, 1.0-1.2 mm, 1.65-1.90 mm respectively; number of whorls up to c. 3 3/8; height aperture up to 0.85 mm; width aperture up to 1.0 mm.
Habitat in Sabah and distribution. Primary forest on sandstone soil. Alt. 1100-1700 m. Sabah: upper Padas River valley; Crocker Range. Endemic to Sabah.
Cross diagnosis. General shape as in K. gregaria, but much smaller (check the diameters of the first three whorls), slightly higher conical and with more convex whorls. The spiral sculpture is generally coarser then in K. gregaria, but may be very inconspicuous in specimens from the Crocker Range (including the illustrated shell which, on the lower surface, has spiral sculpture only near the aperture).
Group 2c. Periphery of last whorl angular in adult shells, or with a peripheral spiral thread. Diameter of the third whorl 2.0 mm or less. Spiral sculpture teleo conch absent or inconspicuously present in patches, only just discernible at 40 times magnification. Figure 70 Helix barrakporensis  Description. Shell small, rather thin, somewhat translucent or opaque, (pale) brown-corneous, (somewhat elongated) conical with almost flat or slightly convex sides; apex narrowly rounded. Surface shiny or with a silky luster. Whorls moderately convex, the last whorl rounded to angular at the periphery, rounded above and below the periphery. Protoconch whorls convex, with spaced, inconspicuous radial riblets and usually subordinate, very fine spiral grooves; protoconch sometimes almost smooth. Teleoconch: Last whorl usually with a peripheral spiral thread coinciding with the suture of the penultimate whorl, above this with very fine, densely and regularly placed radial riblets, often only locally present, in some specimens virtually absent, and with or without traces of very fine (just visible at 40 times magnification), inconspicuous spiral striation; below the periphery usually with numerous fine, moderately and regularly spaced, continuous spiral grooves. Umbilicus open, narrow. Dimensions: Height up to 4.6 mm; width up to 4.3 mm; diameters of the first four whorls 0.65-0.80 mm, 1.10-1.25 mm, 1.5-2.0 mm, 2.15-2.70 mm respectively; number of whorls up to 6 1/2; height aperture up to 1.5 mm; width aperture up to 2.0 mm.
Remarks. Incidental specimens lack the spiral thread along the periphery of the last whorl. A fine but almost continuous spiral striation may be present on the top whorls.  Description. Shell small, rather thin, somewhat translucent or opaque, (pale) yellow-corneous to brown-corneous, (somewhat depressed) conical with convex sides; apex broadly rounded. Surface glossy or shiny. Whorls moderately convex, the last whorl more or less angular at the periphery, rounded above, rounded to almost flat below the periphery. Protoconch whorls convex, with spaced radial riblets and usually subordinate (sometimes equally distinct), very fine spiral grooves; usually these are reduced to spiral rows of minute, shallow identations; often the protoconch is almost smooth. Teleoconch: Last whorl with a peripheral spiral thread coinciding with the suture of the penultimate whorl, above this with very fine, inconspicuous, densely and regularly placed radial riblets locally, or with a few growth lines only; with or without traces of very fine, inconspicuous spiral striation, below the periphery usually with numerous fine, moderately and regularly spaced, continuous spiral grooves which are most distinct towards the periphery. Umbilicus open, narrow. Dimensions: Height up to 2.8 mm; width up to 3.2 mm; diameters of the first four whorls 0.5-0.8 mm, 0.90-1.35 mm, 1.5-2.0 mm, 2.0-2.8 mm respectively; number of whorls up to 5; height aperture up to 1.2 mm; width aperture up to 1.6 mm.
Habitat in Sabah and distribution. Primary and secondary forest on limestone, sandstone and volcanic soil, up to 1400 m alt. Sabah: widespread. Also in Kalimantan. Endemic to Borneo. Cross diagnosis. Adult or nearly adult shells differ from K. barrakporensis by the lower conical spire with more convex sides and a more broadly rounded apex. Usually, the sculpture is less distinct than in K. barrakporensis, and the shells are glossier. Juveniles of both species are sometimes difficult to keep apart.

Kaliella scandens (Cox, 1871)
Habitat in Sabah and distribution. Primary and secondary forest, coastal forest, at 0-1000 m alt, elsewhere to 2000 m alt. Sabah: widespread. Also in Sarawak; Kalimantan. Distribution elsewhere: Vietnam; Thailand; Peninsular Malaysia to Java; Eastwards to Australia, Pacific.
Remarks. Samples from montane environments (e.g. Poring Hot Springs, V 13027 may include shells with a more loosely coiled spire than usual (diameter of the fourth whorl up to 3.0 mm; in other specimens 2.25-2.70 mm). In this character the shells approach K. dendrobates, but the sculpture is typical for K. scandens.
Information on the radula is from Rensch (1932). No Sabah material included in K. scandens has been checked for radula characters. Figure 73 Gunongia dendrobates Tillier & Bouchet, 1988: 269 Description. Shell small, very thin, somewhat translucent, (yellowish) brown, rather low-conical with flat sides; apex rounded. Surface shiny. Whorls moderately convex, last whorl rounded at the periphery (angular in juveniles), rounded above and below the periphery. Protoconch whorls convex, with numerous fine, densely placed radial riblets; spiral sculpture subordinate, very fine (just visible at 40 times magnification) to rather distinct, very densely placed grooves, locally present. Teleoconch: above the periphery locally with fine, slightly spaced, narrow spiral grooves cutting into the crests of the radial riblets and subordinate to these, particularly towards the suture and the periphery; below the periphery slightly coarser and slightly more spaced spiral grooves. Radial sculpture: above the periphery distinct, irregularly spaced and locally crowded, somewhat raised growth lines, next to these areas with fine, densely (slightly more densely than the spiral striation) and regularly placed riblets, on the outer whorls locally interrupted by approximately smooth areas; below the periphery with irregularly spaced, slightly raised growth lines only. Umbilicus open, very narrow. Dimensions: Height up to 3.2 mm; width up to 3.9 mm; diameters of the first four whorls 0.65-0.75 mm, c. 1.1 mm, 1.7-1.8 mm, c. 2.65 mm respectively; number of whorls up to c. 5 1/2; height aperture up to 1.6 mm; width aperture up to 1.9 mm. Animal with an obtuse caudal horn. Radula: central 1-cuspid; laterals and marginals similar, serrate with 2 large cones at the tip and a small in between.
Cross diagnosis. In general shape, sculpture and mode of coiling very similar to K. scandens. Kaliella dendrobates has a much thinner, more shiny shell. The sculpture above the periphery includes irregularly raised growth lines where the fine sculpture of minute radial riblets and even finer spiral grooves is indistinct or entirely absent. In K. scandens raised growth lines are usually absent, and the finer sculpture is continuous. Further differences between the two are found in the radula.
Juveniles of K. dendrobates with a peripheral keel differ from K. calculosa in having a lower conical spire, and a radial sculpture dominated by rather prominent, irregularly spaced, raised growth lines.
We depict a keeled, juvenile specimen with approx. 1 whorl less than the type specimen, which does not have a keel. The sculpture and general shape is similar in both specimens.
The Gunung Trusmadi record is based on a shell consisting of hardly more than a protoconch. Its identity is somewhat uncertain. Figure 74 Helix doliolum Pfeiffer, 1846: 41. Kaliella doliolum (Pfeiffer) Von Moellendorff, 1890Clements et al. 2008Clements et al. : 2762Schilthuizen et al. 2011: 5;Schilthuizen et al. 2013: 544, and Batu Punggul (leg. J.J. Vermeulen, V 1982 Figure 75 Rahula raricostulata auct. Schilthuizen and Vermeulen 2003: 96. Rahula sp. V9667 auct. Clements et al. 2008: 2762 Holotype. Malaysia,Sabah,Sandakan Province,Kinabatangan valley,Batu Pangi (RMNH.5003927). Description. Shell small, rather solid, somewhat translucent to opaque, (pale) brown, conical with convex sides to almost ovoid; apex rounded. Surface shiny. Whorls convex, rounded, suture somewhat imperessed. Protoconch whorls convex, with very fine, densely placed radial riblets starting at some distance from the apex; apex with very fine (just visible at 40 times magnification), inconspicuous spiral striation, which gradually disappears where the radial riblets become more prominent. Teleoconch: Last whorl with a distinct spiral ridge slightly below the periphery, which seems to be the edge of a callus covering the lower surface of the shell, and which continues just above the suture of the penultimate whorl; next to this a fine, dense spiral striation on the lower surface of the shell. Radial sculpture above the spiral ridge consisting of well-spaced (26-33 on the last whorl), coarse, orthocline, approx. straight, high and narrow ribs, which reach down to the spiral ridge and are fused to it, interstices smooth or with an occasional, inconspicuous growth line. Umbilicus closed. Dimensions: Height up to 2.6 mm; width up to 2.1 mm; diameters of the first four whorls 0.5-0.6 mm, 0.8-0.9 mm, 1.1-1.2 mm, 1.35-1.55 mm Cross diagnosis. Differs from Rahula raricostulata (E.A. Smith, 1893) (Sitala raricostulata E.A. Smith, 1893), from Sarawak, by the absence of a distinct, predominant spiral sculpture on the protoconch. Rahula raricostulata has a more conical spire, and fewer radial ribs (11-20) on the last whorl.

Family PUNCTIDAE Morse
Snails. Shell very small, dextral, lenticular or discoid. Sculpture consisting of inconspicuous radial riblets, spiral sculpture subordinate. Aperture without teeth or lamellae, peristome usually thin and not reflected. Umbilicus open, narrow or wide (Family description adapted from Solem 1976Solem , 1988Vaught 1989;Herbert and Kilburn 2004). Habitat and distribution. Soil and litter dwellers. Widely distributed in Africa, Europe, Asia, and Australia.
Remarks. The family is poorly known and although many genera and species have been described, the true diversity may consist of a smaller number of widespread, regionally variable species.
Description. Shell minute, thin, slightly translucent, yellowish brown, low-conical to lenticular, apex rounded. Surface shiny. Whorls well-rounded. Protoconch sculpture: densely placed radial riblets which are particularly distinct towards the periphery; fine, rather densely placed spiral grooves cutting into the crests of the radial riblets. Teleoconch, radial sculpture: locally distinct, widely spaced radial ribs, often with a periostracal crest, which gradually disappear towards the umbilicus; in between these very fine, densely placed, low secondary riblets above the periphery. Spiral sculpture teleochonch: spiral threads, as fine and as densely placed as the secondary radial riblets, above the periphery, grading into widely spaced, rather distinct grooves towards the umbilicus. Umbilicus narrow, 5-6 % of the shell width. Dimensions: height up to 1.1 mm; width up to 1,6 mm; diameter of the first three whorls 0.40-0.45 mm, 0.75-0.80 mm, 1.25-1.30 mm respectively; number of whorls up to 3 3/4, height aperture up to 0.75 mm; width aperture up to 0.90 mm.
Habitat in Sabah and distribution. Secondary forest on sandstone hills, lowland conditions. Sabah: West Coast, one locality known. Endemic to Sabah.
Cross diagnosis. Characterized within the genus by the narrow umbilicus, the presence of radial riblets on the protoconch, and the distinct and widely spaced spiral sculpture on the lower surface.
Etymology. The name refers the the narrow umbilicus [angustus (L.) = narrow]. Remarks. The generic and specific classification of the Subulinidae are still unresolved. Applying Pilsbry 1906[1906-1907 leads to inclusion of the species below in the genus Curvella, but its position is by no means certain.
Zonitidae, subfamily Trochomorphinae, in recent literature (Vaught 1989: 98) raised to family level: Trochomorphidae. The Sabah species are generally known by their shell only. An exception is Trochomorpha rhysa; dissection by Tillier and Bouchet (1988) confirmed its position in the Trochomorphidae.
Generally, the two genera include species with conical shells, not unlike Kaliella Blanford (Helicarionidae) or Philalanka Godwin Austen (Endodontidae), but consistently larger. Several species, for instance G. conicoides, G. labuanensis, and G. scolops, have shells of very characteristic appearance, with a prominent, sharp peripheral keel.

Genus Trochomorpha Albers, 1850
Trochomorpha Albers, 1850: 116;Albers in Albers & Von Martens, 1860: 60. Diagnosis for the Sabah species. Shell rather small to medium-sized, (pale) yellowish green to (yellowish) brown, without any colour patterns, or with lighter or darker streaks following the growth lines; low-conical with flat or slightly convex sides, apex protruding or not. Radial sculpture above the periphery distinct, consisting of riblets or irregularly spaced, raised growth lines locally causing a coarse, irregular wrinkling. Spiral sculpture distinct, consisting of threads which are highest or nodular where crossing the radial sculpture, lower or even absent elsewhere. Umbilicus closed, entirely covered by an extension of the parietal callus of the peristome.
Cross diagnosis. Shares the closed umbilicus with Borneo Geotrochus. We keep the two separate, although the Sabah representatives of both genera have very similar shells. Sabah Trochomorpha is characterized by a coarser radial sculpture on the upper surface of the shell. The spiral sculpture overlies the radial sculpture, forming nodes where the two cross.
Remarks. Possibly, the protoconch with radial riblets can be added to the diagnostic set distinguishing between Borneo Geotrochus and Trochomorpha. Unfortunately, we could not check this for all Borneo Trochomorpha species.
We provide a review of the Sabah species of Trochomorpha.  Description. Shell rather small, thin, opaque, reddish brown with darker brown or whitish streaks following growth lines, slightly paler brown with similar darker streaks below the suture, conical with flat sides; apex not protruding. Surface dull or slightly shiny above the periphery, glossy below. Whorls somewhat convex, outer whorls slightly shouldered; suture impressed, coinciding with the periphery; last whorl distinctly angular and slightly compressed at the periphery, moderately rounded below the periphery. Protoconch (absent in available material). Teleoconch. Radial sculpture: above the periphery irregularly spaced growth lines, developing into locally coarse, irregular wrinkling on the outer whorls, particularly below the suture; below the periphery indistinct growth lines only. Spiral sculpture: last whorl with a peripheral thread; start of fifth whorl above the periphery with 8-9 spiral threads: 3-4 coarse, high and rather narrow threads, with c. 5 minor threads interspersed; all threads highest and most distinct over the raised radial sculpture, low or interrupted in between, at irregular intervals, and with a somewhat erose and locally incised crest; below the periphery a few traces of densely placed, shallow spiral grooves. Umbilicus closed. Peristome not thickened, nor reflexed (see remarks, below). Dimensions: Height c. 8.5 mm; width c. 12.5 mm, h/w c. 0.66; estimated diameters of the first 4 whorls c. 1.2 mm, c. 2.3 mm, c. 4.0 mm, c. 6 mm respectively; number of whorls c. 5 3/4, height aperture c. 4 mm; width aperture c. 7 mm.

Trochomorpha trachus
Habitat in Sabah and distribution. Mixed montane forest, c. 1400 m alt. Sabah: Crocker Range only. Endemic to Sabah.
Cross diagnosis. Uniquely identified by the very coarse, at irregular intervals interrupted spiral sculpture.
Remarks. The material seen is probably sub-adult, and has the apex damaged. The description of the apex and the peristome will need amendation once more material becomes available.
Etymology. The name refers to the shell surface [trachus (Gr.) = rough].  Figure 79 Trochomorpha rhysa Tillier & Bouchet, 1988 Description. Shell rather small, rather thin, about opaque, (pale) yellowish brown to pale greenish brown, moderately low-conical with approx. flat sides; apex not protruding. Surface with a silky luster above the periphery, shiny below. Whorls somewhat convex, outer whorls slightly shouldered; suture impressed, coinciding with the periphery; last whorl distinctly angular but not or hardly compressed at the periphery, rounded below the periphery. Protoconch 2 1/8-2 1/4 whorls, with dense radial riblets except at the apex; transition to teleoconch sculpture abrupt. Teleoconch. Radial sculpture: above the periphery rather densely placed, more or less regularly spaced riblets, slightly more irregular on the last whorl and fading towards the aperture; below the periphery growth lines only. Spiral sculpture: last whorl with a peripheral thread; start of fifth whorl with 14-19 fine, rather low and wide spiral threads or more or less equal strength, forming nodes over the radial sculpture (less distinctly so on the earlier teleoconch whorls), threads on the last whorl dissolving in rows of granules; no spiral sculpture below the periphery. Umbilicus closed. Peristome moderately thickened and reflexed, more distinctly so on the columellar side. Dimensions: Height 6.0-6.8 mm; width 10-12 mm, h/w 0.57-0.62; diameters of the first 4 whorls 1.4-1.5 mm, 2.3-2.5 mm, 3.7-4.0 mm, 5.5-6 mm respectively; number of whorls 5 3/4-6, height aperture 3.0-3.8 mm; width aperture 5-6 mm.

Trochomorpha rhysa Tillier & Bouchet, 1988
Habitat in Sabah and distribution. Montane and sub-alpine forest on sandstone and granodiorite bedrock, 2400-3300 m alt. Description. Shell medium-sized, rather thin, about opaque, yellowish brown, moderately low-conical with somewhat convex sides; apex slightly protruding. Surface with a silky luster above the periphery, shiny below. Whorls: Apical whorls convex, outer slightly convex; suture moderately impressed, coinciding with the periphery; last whorl angular, hardly compressed at the periphery, rounded below the periphery. Protoconch 1 7/8-2 1/4 whorls, with dense radial riblets except at the apex, and a spiral striation cutting into the radial riblets towards the teleoconch; transition to teleoconch sculpture gradual. Teleoconch. Radial sculpture: above the periphery rather densely placed, more or less regularly spaced riblets; below the periphery growth lines only. Spiral sculpture: last whorl with a peripheral thread; start of fifth whorl with 11-14 spiral threads: 2-8 rather distinct, rather low and wide threads but with a narrow crest, which are highest or form nodes over the radial sculpture, and 5-12 similar but less conspicuous threads interspersed; no spiral sculpture below the periphery. Umbilicus closed. Peristome slightly thickened and slightly reflexed, more distinctly so on the columellar side. Dimensions: Height 7.4-10.0 mm; width 14.0-17.0 mm; h/w 0.53-0.59; diameters of the first 4 whorls 1.7-1.9 mm, 3.0-3.3 mm, 5.0-5.5 mm, 7.5-8.2 mm respectively; number of whorls 5 1/2-6 1/8, height aperture 5.0-6.0 mm; width aperture 6.5-8.5 mm.
Habitat in Sabah and distribution. Montane and sub-alpine forest on sandstone bedrock, 1900-3300 m alt. Sabah: Mount Kinabalu only. Endemic to Sabah.
Cross diagnosis. Consistently larger than T. rhysa, and less densely coiled. The sculpture above the periphery is coarser, particularly the radial riblets on the protoconch, as well as the spiral threads on the teleoconch. The latter are also less regularly spaced, and of more unequal strength, with much more inconspicuous threads interspersed in between the distinct ones.
Etymology. The name refers to the knotted shell surface [hapto (Gr.) = to knot; derma (Gr.) = skin].  Description. Shell rather small, rather thin, about opaque, yellowish brown, lowconical with somewhat convex sides; apex protruding. Surface with a silky luster above the periphery, shiny below. Whorls: Apical whorls convex, outer slightly convex; suture hardly impressed, coinciding with the periphery; last whorl acutely angular and compressed at the periphery, rounded below the periphery. Protoconch c. 1 7/8 whorls, with dense radial riblets except at the apex, and a spiral striation cutting into the radial riblets towards the teleoconch; transition to teleoconch sculpture gradual. Teleoconch. Radial sculpture: above the periphery rather densely placed, more or less regularly spaced riblets; below the periphery growth lines only. Spiral sculpture: last whorl with a peripheral thread; start of fifth whorl with c. 13 spiral threads: c. 10 rather distinct, rather low and wide threads but with a narrow crest, which are highest, or form nodes over the radial sculpture, and c. 3 similar but less conspicuous threads interspersed; no spiral sculpture below the periphery. Umbilicus closed. Peristome (not present on the material available). Dimensions: Height c. 6 mm; width c. 11 mm; h/w 0.54-0.55; diameters of the first 4 whorls c. 1.7 mm, c. 2.8 mm, c. 5 mm, c. 8 mm respectively; number of whorls c. 5 1/8, height aperture c. 3.5 mm; width aperture c. 6 mm.
Habitat in Sabah and distribution. Montane forest on sandstone bedrock, 1900-2300 m alt. Sabah: Mount Kinabalu only. Endemic to Sabah.
Cross diagnosis. Similar to T. haptoderma in coiling density and sculpture; differs by having a flatter spire, with a more protruding apex.
Remarks. The only available shell is a juvenile with the last 1/8 whorl broken. The description needs to be amended once more material becomes available.
Diagnosis for the Sabah species. Shell rather small to medium-sized, (pale) corneous to (yellowish) brown, without any colour patterns, or with brown spiral bands (G. spilokeiria with additional white spots and stains); (low) conical with concave, flat or convex sides, apex protruding or not. Radial sculpture above the periphery inconspicuous to distinct growth lines, raised at irregular intervals or not. Spiral sculpture consisting of thin threads, at least some spiral threads close to the periphery usually slightly coarser, the others very fine, often inconspicuous or absent; no spiral sculpture below the periphery. Umbilicus closed, entirely covered by an extension of the parietal callus of the peristome.
Remarks. We provide a review of the Sabah species of Geotrochus. We divide the genus into three informal groups. Group 1a. Suture between the whorls coinciding with the periphery. Shell 13.5-24.5 mm wide in adult specimens. Figure 82 Trochonanina paraguensis E.A. Smith, 1893: 349 Description. Shell medium-sized, rather thin, opaque, uniformly pale yellowish brown, low-conical with flat to slightly convex sides; apex not protruding or only slightly so. Surface with a silky luster above the periphery, shiny below. Whorls: All whorls moderately convex; suture impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, not or hardly compressed at the periphery, moderately rounded below the periphery. Protoconch 1 7/8-2 1/8 whorls, smooth. Teleoconch. Radial sculpture: above the periphery growth lines, raised locally and developing in patches with inconspicuous, somewhat irregularly spaced, fine, low riblets, particularly towards the periphery; below the periphery irregularly spaced growth lines only. Spiral sculpture: last whorl with a sharp but not pinched peripheral ridge; start of fifth whorl with 13-17 well-spaced, very fine and thin spiral threads covering most of the whorl except a narrow strip below the suture, at least some spiral threads close to the periphery usually slightly coarser; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed. Dimensions: Height 6-8.5 mm; width 14-22.8 mm; h/w 0.37-0.42; peripheral keel of the last whorl at 0.39-0.53 of the shell height, measured from the apex; diameters of the first 4 whorls 1.4-1.8 mm, 2.4-2.7 mm, 4.0-4.6 mm, 5.7-6.9 mm respectively; number of whorls 6 3/4-7 5/8, height aperture 3.2-5.2 mm; width aperture 8-11.6 mm.
Cross diagnosis. Characterized by the combination of lack of spiral colour bands, the not-pinched periphery, the moderately convex whorls and lower surface of the shell. (G. labuanensis, G. kinabaluensis, G.

oedobasis).
A group of very similar species, distinguished here on account of shell colour, aperture shape and the position of the peripheral keel relative to the shell height. Anatomical and molecular investigation is needed to further unravel the taxonomical structure of the group.   Figure 83 Helix labuanensis Pfeiffer, 1863: 523. Nanina conicoides (Metcalfe) var. labuanensis (Pfeiffer)   Description. Shell medium-sized, rather thin, opaque, creamy white, greyish very pale yellowish brown, periphery whitish, with a narrow, rather vaguely outlined, pale to dark (ochre-)brown band immediately above it, and often a second, similar band immediately below it, shell low-conical with approx. flat sides, apex not or hardly protruding. Surface shiny. Whorls: Inner whorls moderately convex, outer whorls flat to slightly convex; suture impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, slightly compressed at the periphery, slightly convex below the periphery. Protoconch 2 1/8-2 1/2 whorls, smooth. Teleoconch. Radial sculpture: above and below the periphery scattered inconspicuous growth lines, locally grading into inconspicuous riblets. Spiral sculpture: last whorl with a sharp, slightly pinched peripheral ridge; start of fifth whorl with 4-25 usually well-spaced, low and thin spiral threads, the 2-5 threads close to the periphery more distinct, the others very inconspicuous or absent; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed, basal edge most strongly curved towards the columellar side, and often, to a somewhat lesser extent, towards the periphery; in between only slightly curved. Dimensions: Height 6.3-7.6 mm; width 14.5-17.8 mm; h/w 0.39-0.45; peripheral keel of the last whorl at 0.44-0.54 of the shell height, measured from the apex; diameters of the first 4 whorls 1.3-1.6 mm, 2.2-2.7 mm, 3.6-4.4 mm, 5.2-7.0 mm respectively; number of whorls 6 1/8-6 7/8, height aperture 3.0-3.6 mm; width aperture 7.4-9.2 mm.

Geotrochus labuanensis (Pfeiffer, 1863)
Habitat in Sabah and distribution. Primary and secondary forest on limestone soil. Lives on decaying wood. Sabah: widespread, but scattered localities. More fre quently found in the East part. Endemic to Sabah.
Cross diagnosis. Differs mainly from G. kinabaluensis and G. oedobasis. by the presence of a peripheral colour band (not always present), the slightly pinched periphery, and the less convex outer whorls. The position of the peripheral keel relative to the shell height is intermediate between G. kinabaluensis and G. oedobasis. The spiral sculpture above the periphery is often more widely spaced, and more unequal, with a few stronger threads close to the periphery and very inconspicuous ones, if any, elsewhere.
Remarks. G. labuanensis is a lowland species, contrary to the other species in the group. Description. Shell medium-sized, rather thin, opaque, brown, sometimes a slightly paler brown just below the suture, periphery pale brown to dull white; shell lowconical with approx. flat sides, apex not or hardly protruding. Surface with a silky luster above the periphery, shiny below. Whorls: slightly convex; suture impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, moderately compressed at the periphery, slightly convex below the periphery. conical with almost flat to distinctly concave sides, apex slightly to distinctly protruding. Surface more or less dull or with a silky luster above the periphery, shiny below. Whorls: Apical whorls moderately convex, next whorls approx. flat to slightly convex, outer whorls often flat; suture impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, (distinctly) compressed at the periphery, slightly to rather distinctly concave just below the periphery, slightly to moderately convex towards the umbilical region. Protoconch 1 7/8-2 1/2 whorls, smooth. Teleoconch. Radial sculpture: above and below the periphery inconspicuous growth lines, somewhat raised locally. Spiral sculpture: last whorl with a sharp, distinctly pinched peripheral ridge; start of fifth whorl with 5-17 rather densely placed to somewhat spaced, low and thin spiral threads, the 2-5 threads close to the periphery usually slightly more distinct, the others very inconspicuous or (almost) absent; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed. Dimensions: Height 7.7-10.0 mm; width 16-19.8 mm; h/w 0.42-0.53; peripheral keel of the last whorl at 0.57-0.66 of the shell height, measured from the apex; diameters of the first 4 whorls 1.3-1.5 mm, 2.0-2.5 mm, 2.5-4.0 mm, 4.2-5.6 mm respectively; number of whorls 7-8, height aperture 2.8-3.8 mm; width aperture 8-9.5 mm.
Habitat in Sabah and distribution. Primary and old secondary forest on sandstone and volcanic bedrock, lowland conditions. Living on decaying wood. Sabah, scattered localities: Labuan, Pulau Tiga; Pulau Gaya, Tawau Hills. Also in Sarawak. Distribution: Sumatra. A record from Morotai, Moluccas (Van Benthem Jutting 1941: 23) is probably erroneous.
Cross diagnosis. Generally characterized by the conical spire, but low-conical specimens occur. These approach the G. labuanensis group in general shape but have a more distinctly protruding apex and more distinctly concave sides. Also, relative to the shell height, the peripheral keel is positioned closer to the base of the shell, and the lower surface of the shell is often rather distinctly concave towards the periphery.
See also the remarks under G. scolops.
Group 1b. Suture between the whorls coinciding with the periphery. Shell 10-12.5 mm wide in adult specimens (check also G. oedobasis) Geotrochus spilokeiria Vermeulen, Liew & Schilthuizen, sp. n. http://zoobank.org/648E599B-8DE4-45ED-9F64-DBFD0F938437 Figure 87 Holotype. Malaysia, Sabah, West Coast Province, Crocker Range N.P., Ulu Kimanis, along Keningau-Kimanis road (BOR/MOL 2784). Description. Shell medium-sized, rather thin, opaque, above the periphery greyish with a somewhat vaguely outlined brown band just above the peripheral keel, and with an irregular pattern of white stains and spots which more or less follow the radial and spiral sculpture, periphery white, below the periphery dark brown, grading to white towards the periphery; shell conical with convex sides; apex not protruding. Surface shiny above the periphery, glossy below. Whorls: Apical whorls moderately convex, next whorls slightly convex, slightly shouldered, outer whorl almost flat; suture somewhat impressed in the apical whorls, not so in the outer whorls, coinciding with the periphery; last whorl acutely angular, slightly compressed at the periphery, slightly rounded below the periphery. Protoconch c. 1 5/8 whorls, smooth. Teleoconch. Radial sculpture: above the periphery rather distinct growth lines, raised at irregular intervals; below the periphery indistinct growth lines only. Spiral sculpture: last whorl with a sharp, pinched peripheral keel; above and close to this keel 1 thin, low, sharply outline spiral thread; above this 3-4 very low and wide, vaguely outlined ridges locally visible in tangential light; next to this radial and spiral sculpture oblique rows of very shallow, vaguely outlined indentations are locally visible; below the periphery locally with traces of a fine, shallow, vaguely outlined spiral striation. Umbilicus closed. Peristome not thickened, nor reflexed except on the columellar side (see remarks below). Dimensions: Height c. 8.5 mm; width c. 12.5 mm; h/w c. 0.68; diameters of the first 4 whorls c. 1.5 mm, c. 2.7 mm, c. 4.6 mm, c. 7.0 mm respectively; number of whorls c. 5 5/8, height aperture c. 3.5 mm; width aperture c. 7.0 mm.
Habitat in Sabah and distribution. Disturbed primary forest on sandstone bedrock, c. 1400 m alt. Sabah: Crocker Range only. Endemic to Sabah.
Cross diagnosis. Uniquely identified within Geotrochus by the brown, grey and white mottled shell. The convex sides of the shell, combined with the rapidly expanding whorls are also characteristic.
Remarks. The only shell available is possibly sub-adult. The description of the aperture may need to be amended once more material becomes available.
The pattern of low, vaguely outlined spiral ridges and similar rows of oblique indentations do not occur in any other Geotrochus species.
Etymology. The name refers to the dirty white apiral band [spilos (Gr.) = stained; keiria (Gr.) = bandage].  Description. Shell medium-sized, rather thin, about opaque, brown, above the periphery with a very fine, slightly paler spiral striation, high-conical with concave sides; apex protruding. Surface slightly shiny above the periphery, glossy below. Whorls: Apical whorls moderately convex, other whorls slightly convex, slightly shouldered, last whorl almost flat; suture impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, slightly compressed at the periphery, slightly rounded below the periphery. Protoconch c. 2 whorls, smooth. Teleoconch. Radial sculpture: above the periphery growth lines, slightly raised locally; below the periphery indistinct growth lines only. Spiral sculpture: last whorl with a sharp, somewhat pinched peripheral keel; start of fifth whorl with c. 3 thin, low, widely spaced spiral threads with an irregularly incised crest: 1 slightly more distinct close to the periphery, as well as 2 inconspicuous above these (penultimate whorl with c. 8 such threads, of which 3-4 are slightly more distinct); no spiral sculpture below the periphery. Umbilicus closed. Peristome slightly thickenened, but not reflexed except on the columellar side. Dimensions: Height c. 10.4 mm; width c. 12.5 mm; h/w 0.83-0.84; diameters of the first 4 whorls c. 1.1 mm, c. 1.7 mm, c. 2.2 mm, c. 3.0 mm respectively; number of whorls c. 8 3/8, height aperture c. 3 mm; width aperture c. 6.5 mm.

Geotrochus scolops
Habitat in Sabah and distribution. Forest on sandstone or volcanic soil, lowland conditions. Sabah: Tawau Hills National Park. Endemic to Sabah.
Cross diagnosis. Uniquely identified within Geotrochus by the high-conical shell with concave sides, and tapering towards the apex.
Geotrochus conicoides with a relatively high-conical shell are most similar, but still have a lower h/w-ratio: 0.57-0.66.
Etymology. The name refers to the shape of the spire [scolops (Gr.) = pointed].  Description. Shell rather small, rather thin, about opaque, yellowish brown, whorls slightly darker brown towards the periphery, moderately low-conical with approx. flat sides; apex not protruding. Surface dull or slightly shiny above the periphery, shiny below. Whorls: Apical whorls moderately convex, outer slightly convex, slightly shouldered; suture somewhat impressed, coinciding with the periphery; last whorl acutely angular, slightly compressed at the periphery, rounded below the periphery. Protoconch c. 2 1/8 whorls, smooth (see remark, below). Teleoconch. Radial sculpture: above the periphery rather distinct growth lines, raised at irregular intervals and wrinkling the shell surface, most conspicuously so below the suture, and giving the shell surface a somewhat rough appearance; below the periphery indistinct growth lines only. Spiral sculpture: last whorl with a sharp, somewhat pinched peripheral keel; start of fifth whorl with c. 15 thin, moderately spaced spiral threads: 1-2 slightly more distinct close to the periphery, as well as 13-14 inconspicuous above these; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed. Dimensions: Height c. 5.5 mm; width c. 10 mm; h/w c. 0.55; diameters of the first 4 whorls c. 1.2 mm, c. 2.2 mm, c. 3.3 mm, c. 4.8 mm respectively; number of whorls c. 6 3/8, height aperture c. 3.5 mm; width aperture c. 5 mm.

Geotrochus kitteli
Habitat in Sabah and distribution. Mixed montane forest, 1500-1800 m alt. Sabah: Mount Kinabalu only. Endemic to Sabah. Cross diagnosis. In size and general shape most similar to G. whiteheadi, it differs by the higher ratio h/w, and by the more distinct growth lines above the periphery, which give the shell surface a rough appearance. It differs from Trochomorpha rhysa by its somewhat pinched peripheral keel and the not-nodular spiral sculpture above the periphery.
Remarks. The single shell available is somewhat worn in the apical region. Traces of what may be radial riblets are present in the suture of the protoconch, close to the transition to the teleoconch.
Habitat in Sabah and distribution. Mixed montane forest, 700-2100 m alt. Sabah: Mount Kinabalu only. Endemic to Sabah.

Geotrochus subscalaris
Habitat in Sabah and distribution. Primary, secondary forest and abandoned agricultural land on limestone and sandstone soil, up to 1300 m alt. Sabah: West part, East coast (lower Segama River valley and further South). Endemic to Sabah.
Cross diagnosis. Shell less wide than G. subscalaris, compare shell width and aperture width of both species. Usually, the h/w-ratio is also higher than in G. subscalaris, but here a slight overlap exists.
Etymology. The name refers to the slightly protruding peripheral keel, creating a small notch in between the whorls in lateral view [meristos (Gr.) = divided; trokhos (Gr.) = wheel, often used for the gastropod spire].