The first revision of the carnivorous land snail family Streptaxidae in Laos, with description of three new species (Pulmonata, Stylommatophora, Streptaxidae)

Abstract The family Streptaxidae in Laos is revised. Twelve species are known, mainly from limestone areas, in the genera Discartemon Pfeiffer, 1856, Perrottetia Kobelt, 1905, Haploptychius Möllendorff, 1906, and Indoartemon Forcart, 1946. Three new species, Perrottetia unidentata sp. n. and Perrottetia megadentata sp. n. from northern and central Laos, and Indoartemon diodonta sp. n. from central Laos, are described. All eight species of these three genera previously recorded from Laos are revised and discussed based on examined material from Laos, Cambodia, Vietnam and Thailand. Type material was examined and lectotypes are designated. Details of genital anatomy and radulae are provided, including the first detailed genitalia and radula descriptions from Haploptychius. Two novelties in Streptaxidae, a vaginal caecum, and the occurrence of aphallic individuals, are reported from Haploptychius pellucens (Pfeiffer, 1863).

Early classifications of the family such as W. Kobelt (1905-6), used mainly shell shape and the arrangement of apertural dentition. However, many shell characters are highly conserved or occur recurrently, making some species and genera difficult to separate. Fortunately, the reproductive organs of streptaxids can also be taxonomically significant (e.g. Schileyko 2000, Rowson and Tattersfield 2013, Siriboon et al. 2013, 2014a. Few reports have contributed data on the genitalia of Southeast Asian taxa (e.g. Stoliczka 1871, Berry 1963, 1965 until recently (Siriboon et al. 2013, 2014a, b, Páll-Gergely et al. 2015. In Indochina, streptaxid diversity was throught to comprise only 10 genera and about 40 species (Bruggen 1967). However, in the last decade 21 new species (more than half the previous total) and one new genus have been described from Indochina (Siriboon et al. 2013, 2014a, b, Do and Do 2015. Thirty-seven species are recorded from Thailand (Panha 1996, Hemmen and Hemmen 2001, Siriboon et al. 2013, 2014a, 10 from Myanmar (Blanford and Godwin-Austen 1908), and 45 from Vietnam (Schileyko 2011). In contrast, only three species were reported from Laos in the past two centuries (Pfeiffer 1863, Möllendorff 1898, with three others added in recent years (Schileyko 2011, Do andDo 2015).
Almost all groups of the land snail fauna in Laos have been less-well studied than those of neighbouring areas. The Lao People's Democratic Republic, until recently encompassed some of the most significant forest areas remaining in Southeast Asia such as mountainous areas in the north and limestone karsts in central area, and some of the most intact biota left in Asia (Kemp 2011). Those habitat characteristics also harbor diverse of terrestrial molluscan fauna. The present paper focuses on the four genera, Discartemon Pfeiffer, 1856, Perrottetia Kobelt, 1905, Haploptychius Möllendorff, 1906, and Indoartemon Forcart, 1946 that were formerly recorded from Laos. Genital anatomy and shell micro-structures of are carefully investigated. The type specimens of all known species were examined, and the penial hooks and radula morphology of Haploptychius are defined for the first time. This adds significantly to knowledge of the Streptaxidae in Indochina and especially in Laos.

Materials and methods
Animals were collected from evergreen forest in the north, and limestone karsts and dipterocarp forest in the south of Laos. Live specimens were photographed Type species. Streptaxis sinensis Gould, 1859, by original designation.
Description. Shell depressed to very distorted, mostly white-hyaline or transparent. Shell surface smooth and glossy or with fine radial ridges. Embryonic shell smooth; following whorls increasing regularly; penultimate whorls slightly to strongly extended beyond body whorl. Last whorl rounded and more or less deviated from the vertical axis. Umbilicus narrowly open and deep. Aperture sub-circular to semi-ovate. Peristome expanded and reflected. Apertural dentition always consisting of a single parietal lamella. Schileyko (2000) includes species with a "smooth" parietal wall, i.e. without a lamella in Haploptychius, but whether such taxa belong in this genus requires further investigation.
Live specimens exhibit a semi-transparent bright yellow body, sometimes with brownish spots; skin reticulated. Upper tentacles yellow to orange, long, with black eye-spot on tip; lower tentacles short. Brownish digestive gland and black kidney may be visible through transparent shell. Foot narrow, undivided and with short tail.
Genitalia with long and slender penis; penial sheath long, about a half to whole length of penis. Internal wall of penis with numerous long and slender penial hooks in longitudinal arrangement. Vas deferens passes under penial sheath before connecting apically to penis. Vagina and free oviduct short. Seminal vesicle present, convoluted and short. Vaginal hooks not found.
Remarks. Currently, the genus Haploptychius consists of about 40 nominal species distributed from India to Indochina, south of China and Greater Sunda Islands (Kobelt 1906, Zilch 1961, Richardson 1988, Schileyko 2000. Fifteen species were reported from Indochina, of which only three species: H. pellucens (Pfeiffer, 1863), H. porrectus (Pfeiffer, 1863) and H. fischeri (Morlet, 1887) were recorded from Laos (see Gude 1903, Kobelt 1906, Schileyko 2011. General shell morphology of Haploptychius is quite similar to Oophana Ancey, 1884 andIndoartemon Forcast, 1946. However, it differs in having only a parietal lamella; while Oophana usually has parietal, palatal, columellar and basal lamellae, and Indoartemon always has parietal and basal lamellae. In addition, the genitalia of Haploptychius have a penial sheath extends about a half to entire the penis length, vas deferens passes through penial sheath, and long slender penial hooks. In Oophana, the vas deferens enter the penial sheath apically with very short vagina (Berry 1963, Schileyko 2000; and Indoartemon, the vas deferens attached (not pass through) the penial sheath, with small and short penial hooks (Siriboon et al. 2013).
Carinartemis Siriboon & Panha, 2013 resembles Haploptychius in having only a parietal lamella. However, it differs from Haploptychius in its very sharp peripheral keel and having the last whorl more deviated from the vertical axis. In addition, the genitalia has thick or thin penial sheath, penial hook short and stout, and vaginal hooks present (Siriboon et al. 2014b).

Haploptychius pellucens
Material examined. This species was described from the H. Cuming collection. An illustration of the shell and one set of measurements were given in the original description. Three specimens from the Cuming collection at NHM have Pfeiffer's handwritten label stating the species name and locality. In order to stabilise the name, an identical specimen matching with the illustration and measurements given in the original de- Description. Shell. Shell oblique-ovate, white and translucent. Whorls 6½, spire conical with distinct suture. Shell surface glossy with thin transverse ridges which diminish below periphery. Embryonic shell about 2½ whorls, with smooth surface; following whorls regularly coiled. Penultimate whorl and last whorl rounded, axially deflected. ferentiated, lanceolate, unicuspid. Latero-marginal teeth gradually reduce in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 10G).
Genital organs. Atrium (at) short. Proximal penis (p) stout about one-thirds of penis length; distal penis slender. Penial sheath (ps) thin, extending about half of penis length; penial sheath retractor muscle (psr) very thin, originating at atrium and inserted apically at penial sheath (Fig. 6A). Vas deferens (vd) passes through about one-third of penial sheath length before entering into penis apically. Penial retractor muscle (pr) very thick and connected at penis apically (Fig. 7A, B).
Vagina (v) short, about one-third of penis length. Gametolytic duct (gd) long tube extending to albumin gland; gametolytic sac (gs) ovate. Free oviduct (fo) proximally large with almost equal diameter to vagina, becoming narrower distally. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club-shaped. Hermaphroditic duct (hd) bearing long and thin seminal vesicle. Seminal vesicle (sv) about three times longer than the length from talon to branching point of seminal vesicle (Fig. 7A).
Vaginal wall with series of transverse and undulated parallel vaginal folds; vaginal hooks absent (Fig. 9F).
Distribution. This species is known from several limestone areas from central to northern part of Laos. The animals can be found at altitudes from 150-300 meters above mean sea level.
Remarks. This species can be distinguished from H. porrectus by having a larger shell, more elevated spire elevated and less oblique aperture. The vas deferens passes through a shorter part of the penial sheath length, and the vagina wall has undulated transverse ridges rather than papillae. Haploptychius pellucens can be distinguished from H. costulatus (Möllendorff, 1881) from China by having a larger and thinner shell, narrower umbilicus andhaving the left periphery of the penultimate whorl extending beyond the diameter of the last whorl. Haploptychius fischeri differs from this species by having a larger, more depressed and thicker shell, with a more obtuse spire, and subquadrangular aperture (Fig. 3G).
All live adult specimens were dissected and the genitalia have been examined, and three different types of genitalia are observed. There are six fully adult specimens collected from Nam Ork Roo, Oudomxay with 'normal' genitalia ( Fig. 8A). Two specimens from Ban Namone, Xayabouly have no male genital organs (penis, retractor muscle, vas deferens and prostate gland), while female genital organs are well developed and fully function (Fig. 8D). This is apparently the first report of aphallic animals in Streptaxidae. The other two specimens from Ban Namone, have a 'normal' penis, but have an enlarged and curved "vaginal caecum (vc)" near the penis and atrium junction (Fig. 8B, C). This too is an unusual or unique structure in Streptaxidae. Nevertheless, all these animals appear conspecific based on their shells and the causes of this variation are unknown. Material examined. This species was described from the H. Cuming collection. The number of specimens was not indicated, but only one set of measurements was given in the original description. The NHM collection contains two specimens from the Cuming collection that has Pfeiffer's handwritten label stating the species name and collection locality. In order to stabilize the name, a specimen matching with the measurements given in the original description is designated here as lectotype NHMUK 20140750.1 ( Description. Shell. Shell oblique-heliciform, white and translucent. Whorls 6½, spire conical, suture distinct. Shell surface glossy, with transverse ridges that diminish below the periphery. Embryonic shell smooth with 2½ whorls; following whorls regularly coiled. Penultimate whorl rounded; last whorls rounded and axially deflected. Aperture subcircular; peristome thickened and reflected. Aperture dentition with one parietal lamella. Umbilicus open and deep ( Fig. 3D-F).
Genital organs. Atrium (at) short. Proximal penis (p) stout about one-fifth of penis length; distal penis slender. Penial sheath (ps) thin, extending about two thirds of penis length; penial sheath retractor muscle (psr) very thin, originating at atrium and inserting distally on penial sheath (Fig. 7C). Vas deferens (vd) passes through about a quarter of the penial sheath length before entering into penis apically (Fig. 7D). Penial retractor muscle (pr) thick, short and connected with penis apically.
Vagina (v) short, about half of penis length. Gametolytic duct (gd) long tube extending as far as albumin gland; gametolytic sac (gs) small. Free oviduct (fo) short with almost the same diameter as vagina. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small and club shape. Hermaphroditic duct (hd) bearing very long and enlarged seminal vesicle (sv) about ten times longer than the length from talon to branching point of seminal vesicle (Fig. 7C).
Distribution. This species is known from the limestone outcrops in northeastern and central parts of Laos. The animals can be found at altitudes from 150-300 meters above mean sea level.
Remarks. This species can be distinguished from H. dorri (Dautzenberg, 1894) and H. blaisei (Dautzenberg & Fischer, 1905) in having a less depressed shell and less deviated last whorl. In addition, H. blaisei possesses a solid shell with an angular penultimate whorl, and H. dorri has a smaller and smooth shell with an angular penultimate whorl. Haploptychius anceyi (Mabille, 1887) is similar to H. porrectus, however it differs in its smaller shell, circular aperture, and nearly smooth shell surface. Material examined. The species was described based on material from Jourdy's collection and an illustration was included in the original description (Morlet 1887: 259, pl. 12, fig. 1, 1a). There is a single specimen from L. Morlet in the MNHN collections with an original label stating "Type". In order to stabilize the name, a shell that matched well with the illustration and measurements given in the original description is designated here as lectotype MNHN-IM 200030873 (Fig. 3G).

Haploptychius blaisei
Haploptychius blaisei is superficially similar to H. diespiter (Mabille, 1887) and H. dorri from north Vietnam, but it has a larger shell, more depressed spire, rounded penultimate whorl, a wide and deep umbilicus, and thin transverse ridges on the upper periphery. For comparison, H. diespiter (Fig. 4B) has the last whorl less deviated from the vertical axis, and H. dorri (Fig. 4C) has a more depressed suture.

Remarks. The genus
Perrottetia differs from all other Southeast Asian streptaxid genera in having two longitudinal furrows outside the aperture. Apertural dentition usually comprises one or two parietal lamellae, plus, palatal, basal and columellar lamellae. Genitalia with long penis, penial hooks present, and vaginal hooks sometimes present (Zilch 1960, Schileyko 2000, Siriboon et al. 2013. Currently, 29 Perrottetia species are recognized, from India and Sri Lanka to Indochina and southern China (Kobelt 1906, Richardson 1988, Schileyko 2011, Siriboon et al. 2013. Two species have been reported from Laos, P. dugasti (Morlet, 1892) and P. daedaleus (Bavay & Dautzenberg, 1908) (see Schileyko 2011). Material examined. The species was described based on material from L. Dugast collection but no illustration was given. Morlet (1893: 315, 316, pl. 7, fig. 5, 5a, 5b) subsequently published the description and illustrated a single specimen. There is a specimen of L. Morlet in the MNHN collections with an original label stating "Type". In order to stabilise the name, the shell that closely matched with the measurements given in the original description and illustration in Morlet (1893: pl. 7, fig. 5, 5a, 5b) is here designated as lectotype MNHN-IM 200030867 (Fig. 4A).
Remarks. Shell sub-oblique heliciform with depressed spire and 6 whorls. Shell surface smooth, glossy and with a distinct suture. Embryonic shell smooth, following whorl regularly expanded. Last whorl rounded, axially deflected, with longitudinal furrows present. Aperture narrow; peristome discontinuous, thick and expanded, and short sinulus present. Aperture dentition consisting of two parietal lamellae (lower one large; upper one small and close to sinulus), one palatal lamella, one basal lamella and one bifid columellar lamella.
Compared with P. messageri (Bavay & Dautzenberg, 1908), this species differs in having a strong lower parietal lamella, a bifid columellar lamella, and the left periphery of penultimate whorl not extended beyond the diameter of the last whorl. In contrast, P. messageri has a strong columellar lamella, a supracolumellar lamella is present, and the left periphery of the penultimate whorl extended beyond the diameter of the last whorl (Fig. 5D).

Fig. 5C
Streptaxis daedaleus Bavay and Dautzenberg 1908: 230 Remarks. Shell suboblique-heliciform with a convex spire and 6 whorls. Shell surface with strong transverse ridges running continuously to umbilicus. Embryonic shell with thin transverse ridges and following whorl regularly expanded. Last whorl rounded, axially deflected, longitudinal furrows present. Aperture triangular; peristome discontinuous, thickened, broadly expanded and sinulus absent. Apertural dentition with two parietal lamellae (lower one small; upper one large and close to sinulus), one angular lamella, one palatal lamella (located far inside aperture) and one columellar lamella.
This species is superficially similar to P. mabillei (Bavay & Dautzenberg, 1903) in having strong transverse ridge over the entire shell, but P. daedaleus has a large upper parietal lamella, a palatal lamella located inside the aperture, and strong columellar lamellae, while P. mabillei (Fig. 5B) has a large lower parietal lamella and bifid columellar lamellae.

Perrottetia aquilonaria Siriboon & Panha, 2013 Figs 1, 5E
Perrottetia aquilonaria Siriboon et al. 2013: 50-52 Remarks. Perrottetia aquilonaria was described from several localities in the northern part of Thailand with a complete information on shell, radula and genitalia. The specimens collected from limestone outcrops in Borkeo and Phongsaly of Laos have both shells and genitalia that match very well with this species. Laos specimens seem to differ only in the slightly smaller shell, therefore we treated them as the same species.
Perrottetia aquilonaria can be distinguished from P. dugasti and P. messageri from Vietnam by having a depressed spire, shouldered last whorl, thin parietal callus and upperparietal lamella separated at a right angle. In contrast, P. dugasti has a rounded last whorl and a small upper-parietal lamella located deeper inside the aperture, and P. messageri has paralleled parietal lamellae, a small supercolumellar lamella is present, and the left side of the penultimate whorl extended beyond the diameter of the last whorl (Fig. 5A, D).
Diagnosis. This new species differs from P. daedaleus, P. aquilonaria, P. dugasti and P. messageri from Vietnam in having an oblique shell, a single parietal lamella, widely expanded lip, the last whorl strongly axially deflected, the left side of penultimate whorl well extended beyond the diameter of last whorl, and the distal end of penis with a wing-like structure. The other four species have two parietal lamellae, the last whorl little axially deflected and the left side of penultimate whorl not extended beyond the diameter of the last whorl. For further comparison, P. daedaleus has an elevated spire, transverse ridges over the entire shell and a basal lamella located deep inside aperture (Fig. 5C); P. aquilonaria has a smaller shell, elevated spire, bifid columellar lamella, and genitalia with atrial pores and vaginal hooks absent (Fig. 5E); P. dugasti and P. messageri have a smooth shell surface, a bifid collumella lamella and a supracolumellar lamella (Fig. 5A, D). Perrottetia gudei from north Vietnam differs from the new species in having an elevated spire, in being less deviated from the vertical axis, and in having thin transverse ridges (see Siriboon et al. 2013).
Description. Shell. Shell oblique-heliciform, semi-transparent; whorls 6½, spire weakly convex with distinct suture. Shell surface glossy with strong transverse ridges on upper shell surface. Embryonic shell large, about 2½ whorls, with a smooth surface; following whorls regularly coiled. Shell periphery shouldered; last whorl axially deflected; two deep longitudinal furrows present. Aperture semi-ovate; peristome discontinuous; parietal callus thin; lip thickened, broadly expanded and slightly reflected. Apertural dentition with one large, strong and sinuous parietal lamella, one small upper palatal lamella, one palatal lamella, one large basal lamella, one strong columellar lamella, and one small supracolumellar lamella. Umbilicus widely open and shallow ( Fig. 5F-I).
Genital organs. Atrium (at) short. Proximal penis (p) long and slender; distal part near retractor muscle with an expanded wing-like structure (a flat blade on either side of the penis, each about one-tenth of penis length). Penial sheath (ps) thin and extending about one-third of penis length; penial sheath retractor muscle (psr) very thin, originating at atrium and inserting distally on penial sheath (Fig. 7E). Vas deferens (vd) passes through about one-third of penial sheath length before entering into penis apically (Fig. 7F). Penial retractor muscle (pr) thin and long, inserted at penis and vas deferens junction.
Vagina (v) short, about one-tenth of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Free oviduct (fo) long and cylindrical with equivalent diameter to vagina, tapering distally. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) very small, short and club shape. Hermaphroditic duct (hd) bearing very short and thin seminal vesicle (sv) about one and half times longer than the length from talon to branching point of seminal vesicle (Fig. 7E).
Vaginal wall with transparent vaginal hooks (about 10 hooks/200 μm 2 ). Hooks located on low conical vaginal papillae. Vaginal hooks small (< 0.1 mm in length), short and expanded at base; tips pointed and straight to slightly curving away from genital orifice (Fig. 10E, F).
Etymology. The specific epithet "unidentata" derived from the Latin words "unus" meaning "one" and "dens" meaning "tooth". It referred to a single parietal lamella (or teeth) of the new species.
Distribution. This species is known only from the type locality, Houaphanh, a limestone karst area.

Perrottetia megadentata
Type locality. The limestone outcrop at Ban Phone Can, Yommalat, Khammouan,Laos (17°31'35.6"N,105°9'40.7"E) Diagnosis. The characters distinguishing Perrottetia megadentata sp. n. from P. daedaleus, P. aquilonaria, P. dugasti and P. mabillei are a single large parietal lamella, the absence of a palatal lamella absent and the presence of an infra-columellar lamella. The other four species have two parietal lamellae and a palatal lamella. Furthermore, P. dugasti and P. aquilonaria have a smooth shell, slightly depressed spire, and a bifid columellar lamella (Fig. 5A, E). Perrottetia daedaleus and P. mabillei have strong transverse ridges over the entire shell, a palatal lamella, and a bifid basal lamella, a columellar lamella is absent in P. mabillei (Fig. 5B), while one basal and one columellar lamella are present in P. daedaleus (Fig. 5C). The new species differs from P. unidentata sp. n. in its ovate shape, smooth shell surface, thicker shell, in the absence of a palatal lamella, and in having infra-and supra-columellar lamellae. The new species is superficially similar to P. dermapyrrhosa Siriboon & Panha, 2013, but is distinguished by having a single and large parietal lamella, and in the absence of a palatal lamella.
Description. Shell oblique-ovate, white and translucent; whorls 6, spire conical, with distinct suture. Shell surface glossy with transverse ridges near suture. Embryonic shell large, about 2½ whorls, with a smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected; two shallow and short longitudinal furrows present. Aperture subcircular, peristome continuous; parietal callus thickened; lip thickened, expanded and reflected; short sinulus present. Apertural dentition with very large and strong sinuous parietal, one large basal lamella located deep inside aperture, one small infracolumellar lamella, one large columellar lamella, and one small supracolumellar lamella. Umbilicus widely open and deep (Fig. 6A, B) Etymology. The specific epithet "megadentata" is derived from the Greek word "mega" meaning "large" and the Latin word "dens" meaning "tooth". It referred to the single large parietal lamella of the new species.
Distribution. This species is known only from the type locality in central Laos.

Remarks.
To date no living specimens have been collected.
Remarks. The genus Indoartemon can be recognized by the dentition, which consists of one parietal and one palatal lamella (a basal lamella is also present in some species). The penis is long, with a thin penial sheath extending about half of the penis length, through which the vas deferens does not pass. Penial hooks are present (Siriboon et al. 2014b).
Currently, ten species are recognized, of which seven were reported from Indochina south of China and Hainan. Only one species, I. tridens (Möllendorff, 1898) has previously been recorded from Laos (Richardson 1988, Schileyko 2000, Siriboon et al. 2014b); here we describe another.
Remarks. Shell oblique-ovate with 5½ whorls, semi-transparent, spire slightly convex, with distinct sutures. Shell surface glossy white with thin growth lines; following whorls regularly coiled. Last whorl axially deflected. Aperture triangular; peristome con- tinuous; lip thickened, little expanded and slightly reflected. Apertural dentition with one large parietal lamella, one palatal lamella, and one small bifid columellar lamella.
Only the type specimen was examined. Indoartemon tridens differs from I. eburneus, I. prestoni (Gude, 1903) and I. medius Siriboon & Panha, 2014 from Thailand by having a bifid columellar lamella, an ovate-heliciform shape, its smooth shell surface, narrow umbilicus, and having the left side of penultimate whorl extended beyond the diameter of last whorl. For comparison, I. eburneus and I. prestoni have a less deviated last whorl, transverse ridges on the shell, and a widely open umbilicus; I. medius has an angular penultimate whorl and strong transverse ridges.
Description. Shell. Shell oblique-heliciform, white and translucent; whorls 6½-7, spire conical, with distinct suture. Shell surface dull, with fine transverse ridges that diminish below the periphery. Embryonic shell large, about 2½ whorls, with smooth surface; following whorls regularly coiled. Last whorl shouldered, axially deflected, and not expanded. Aperture subcircular; peristome continuous, parietal callus thickened; lip thickened, expanded and little reflected. Apertural dentition with one large and strong parietal and one small palatal lamellae. Umbilicus narrow and deep (Fig. 6D-F).
Etymology. The specific epithet "diodonta" is derived from the Greek words "di" meaning "two" and "odontos" meaning "tooth", referring to the dentition of the new species.
Distribution. This species is known from limestone karst in Khammouan Province, central Laos. The animals can be found at altitudes up to 140 meters above mean sea level.
Remarks. To date no living specimens have been collected.

Discussion
This study increases the number of streptaxid species recorded from Laos to twelve, three of which are new. Streptaxids occur in both limestone and non-limestone areas in the central and northern parts of Laos. The fauna apparently remains less diverse than that of Thailand and Vietnam (Panha 1996, Hemmen and Hemmen 2001, Siriboon et al. 2013, 2014a, b, Schileyko 2011. The highly modified habitats of southern and some central areas of Laos may harbour a lower species diversity. For example, Indoartemon tridens was recorded in 1898 by Möllendorff from its type locality at Boloven plateau, Paksong, Champasak, Laos, but our surveys yielded no specimens collected from this locality. The species can be separated by geography, shell morphology, and (where available) genital anatomy. Two species from the genus Haploptychius; H. pellucens and H. porrectus were described from Laos by Pfeiffer (1863). From our results living and shells specimens of H. pellucens and H. porrectus were collected from nine sampling sites in six provinces such as Louang Namtha, Oudomxay, Louang Phrabang, Xayabouly, Bolikhmaxay and Xieng Khaung. Shell morphology and genitalia anatomy were compared between the two species. The two can be separated by having different shell size and shape, as well as differences in the penial sheath, penial hooks, and vaginal wall. The southernmost population of H. pellucens is particularly small. Most records of Haploptychius species are from northern Laos, latitude 18°-21°.
Perrottetia unidentata sp. n. and P. megadentata sp. n. are the first two species of the genus recorded in Laos, and are geographically and altitudinally separated. Perrottetia unidentata sp. n. occurs in northern Laos close to the Lao-Vietnam border at over 700 m above sea level, while P. megadentata sp. n. occurs far to the south and lower than 200 m above sea level (Fig. 1). The two species can be separated by shell morphology. Perrotettia has been collected from central to northern Laos, latitude 18°-22°.
Indoartemon diodonta sp. n. is the second species of this genus recorded from Laos after I. tridens (Möllendorff 1898). The new species was found in central Laos, while the first was found in southern Laos, at over 1000 m above sea level. In Laos, Indoartemon has now been recorded between latitude 14°-18°.