Genus-level revision of the Alycaeidae (Gastropoda, Cyclophoroidea), with an annotated species catalogue

Abstract 412 species-group names (including 11 replacement names), and 14 genus-group names of the Alycaeidae have been introduced to date. Type materials of 85% (336) of the known species and subspecies were examined, a further 5% (19) of the taxa were studied using available non-type material, and for another 6% (22) the original descriptions were sufficiently detailed to evaluate their taxonomic status. Only 3% of the taxa (12) could not be examined. Special attention was paid to the sculpture of the embryonic whorls and the sutural tube-microtunnel system in order to provide a novel classification for this group. In this study 363 taxa (320 species or 43 subspecies) are accepted within the family Alycaeidae. Of these, 22 have been described by the lead author and his coauthors in previous publications. In addition, there are 18 species that were formerly classified in Cycloryx and now belong to Pincerna due to its synonymy with Cycloryx. Among the remaining 323 species, 209 (65%) are transferred here to another genus, whilst 114 (35%) have remained in their original genus. Seven genera are accepted. While some questions (e.g., the distinction between Pincerna and Alycaeus) remained unanswered, this revision made three main achievements: (1) The Dicharax species were identified based on the absence of spiral striation on the entire shell; (2) the Metalycaeus species were identified based on the spiral striation of the protoconch; (3) and Stomacosmethis was separated from Alycaeus based on the extremely short sutural tube. Five nominal species are being synonymised with other species, and eight species are now treated as subspecies. The following replacement names are proposed: Dioryx urnula niosiensis Páll-Gergely, nom. nov. for Alycaeus urnula var. daflaensis Godwin-Austen, 1914; Dioryx urnula rotundus Páll-Gergely, nom. nov. for Alycaeus urnula var. globosus Godwin-Austen, 1914; Pincerna crenilabris juttingae Páll-Gergely, nom. nov. for Alycaeus crenilabris laevis van Benthem Jutting, 1959; Pincerna crenilabris korintjiensis Páll-Gergely, nom. nov. for Alycaeus crenilabris latecostatus van Benthem Jutting, 1959; Dicharax conicus jatingaensis Páll-Gergely, nom. nov. for Alycaeus conicus var. nanus Godwin-Austen, 1914; Metalycaeus godwinausteni Páll-Gergely, nom. nov. for Alycaeus neglectus Godwin-Austen, 1914; and finally Metalycaeus suhajdai Páll-Gergely, nom. nov. for Alycaeus varius Godwin-Austen, 1914.


Introduction
The Alycaeidae are operculate land snails in the superfamily Cyclophoroidea. Approximately 360 Asian species and subspecies have been described so far, and classified into 14 genera or subgenera. Alycaeids inhabit a vast area that stretches from the Western Ghats (India) through the Himalaya to Japan in the east, the Chinese Gansu and Shaanxi provinces in the north and Indonesia to the south (Godwin-Austen 1882-1920Gude 1921;van Benthem Jutting 1948, 1959Minato 1988;Gittenberger et al. 2017;Aravind & Páll-Gergely 2019). The alycaeid shell is characterised by a tube, which is closed at its outer end, and opens into the inside of the shell just behind the operculum. This tube is in contact with numerous, extremely narrow tunnels, which are formed by the outermost shell layer (Páll-Gergely et al. 2016).
Some terrestrial caenogastropod genera lacking such a sutural tube have provisionally been assigned to the Alycaeidae. Laotia Saurin, 1953, which includes two species, has been included either in the Diplommatinidae, because of its similarity with Helicomorpha, or in the Alycaeidae, because of its resemblance to the alycaeid Chamalycaeus (Saurin 1953;Páll-Gergely 2014). The latest publication on Laotia placed this genus in Alycaeidae (Do et al. 2015). The Madagascan endemic Boucardicus Fischer-Piette & Bedoucha, 1965(Madecataulus Fischer-Piette & Bedoucha, 1965 is a synonym, see Emberton and Pearce 1999) has also been placed in Alycaeidae due to a similar shell shape and radula (Emberton 2002;Egorov 2019). Following recent extensive surveys, there are now approximately 200 accepted Boucardicus species (Fischer-Piette et al. 1993;Emberton and Pearce 1999;Emberton 2002;Emberton et al. 2010;Balashov and Griffiths 2015).
Our study covers the systematics of the Alycaeidae sensu stricto, a group that is characterised by the possession of an external tube that runs along the suture (see above). Although anatomical and radular characters are known for some species (Godwin-Austen 1882-1920Tielecke 1940;Venmans 1956;Emberton and Pearce 1999;Emberton 2001), those can only be used as supplementary information to hypothesise about the relatedness of the genera, and cannot be used for the appropriate generic placement of species at the current time. Thus, the classification presented here is primarily based on morphological characters of the shell.
The current generic subdivision of the Alycaeidae was established over a century ago and no genus-level revision has been proposed since the publication of Kobelt's (1902) monograph. Arguably, most authors did not examine the type species of genera, especially those of Alycaeus, Chamalycaeus and Dicharax, when attributing new alycaeid species to any of these genera. Moreover, some allegedly diagnostic characters of the genera and subgenera may not reflect evolutionary relationships because these character states have probably evolved in convergence. For example, the low spire was regarded as the key trait of Chamalycaeus (Kobelt 1902). However, most Chamalycaeus, Metalycaeus and Dicharax species are low-spired, and even Alycaeus jousseaumei has a depressed shell, while, there are Dicharax and Metalycaeus species that are high spired . Similarly, Dicharax was defined on the basis of a swelling behind the peristome (Kobelt 1902). This trait, however, occurs in several species of the genera Metalycaeus and Dicharax, and the strength of the swelling is very variable across Dicharax and Metalycaeus species . Lastly, the outer surface traits of the operculum, which defined the genera Pincerna, Stomacosmethis and Metalycaeus, are also variable within species, and, on the other hand, show similar morphology between species not closely related.
The aim of this study is to provide an updated generic classification of the Alycaeidae based on the principles of our former paper ) focusing on two key traits largely neglected in previous publications, because these are presumed to be more useful to distinguish natural groups. Firstly, the sculpture on the outer shell surface and secondly, the length and sculpture of the area where the sutural tube is situated and the surface is differently ribbed from the other whorl range. Microtunnels functioning as complex gas exchange device are present with the sutural tube, which could provide useful traits for alycaeid systematics, at least in some of the groups (Páll-Gergely et al. 2016).

Taxonomic history of Alycaeidae
Pfeiffer (1858) divided the fourteen species of the genus Alycaeus (equivalent to present-day Alycaeidae) known at the time into two informal groups, namely a species with subturbinate shells ("Subturbinati") and those with depressed shells ("Depressi"). Benson (1859) named three sections within Alycaeus as follows. (1) Alycaeus: "the last whorl constricted somewhat remotely from the aperture, tumid on both sides of the constriction"; (2) Charax: "constriction broad, contiguous to the aperture, and divided more or less remotely from it, across the whorl, by a ridge which is hollow internally"; (3) Dioryx: "constriction narrow, and immediately behind the aperture; the sutural tube arising proportionally nearer to the peristome than in Alycaeus and Charax". In Benson's (1859) system, all the three groups were further sub-divided into unnamed subgroups on the basis of shell shape (Alycaeus and Dioryx) and the morphology of the swelling between the constriction and the aperture (Charax). Pfeiffer (1876) introduced the name Orthalycaeus as a subgenus of Alycaeus and divided it into four subgroups. The name was established without description, but contained 26 species, which made it available. Pfeiffer seemingly intended this name to be used as what we would call today a nominotypical subgenus. He did not select a type species, which was subsequently done by Kobelt (1879: 191), who selected Alycaeus gibbus as the type species of Orthalycaeus. Because this species is also the type species of Alycaeus (also by subsequent designation), these two genus names are objective synonyms. Kobelt and Möllendorff (1897) recognised two genera within the family Alycaeidae: Dioryx and Alycaeus (with the subgenera Orthalycaeus, Chamalycaeus, Charax). Kobelt's (1902) monograph was based on the same system as the one by Kobelt and Möllendorff (1897), but he treated the Alycaeinae as a subfamily of the Cyclophoridae. Kobelt (1902) recognised Dioryx as a distinct genus and subdivided Alycaeus into four 'sections': Alycaeus, Chamalycaeus Kobelt & Möllendorff, 1897 (incorrect attribution of authors, see under Chamalycaeus), Dicharax Kobelt & Möllendorff, 1900 (replacement name for Charax Benson, 1859, non Charax Scopoli, 1777) and Metalycaeus . Metalycaeus was described for two Japanese species (A. melanopoma and A. hirasei). Later, A. tsushimanus was also included in Metalycaeus (Pilsbry & Y. Hirase, 1909a). Metalycaeus has only been reported from Japan, and was diagnosed on the basis of a thickened ring on the outer side of the operculum. In later publications it was not accepted as a distinct taxon, but treated as a junior synonym of Chamalycaeus (see Minato 1988). Preston (1907) described the subgenus Pincerna for Alycaeus (Pincerna) liratula Preston, 1907. According to Preston Pincerna has an alycaeiform shell, which is higher than wide, and the operculum with a "circular cup" on its outer surface. The subgenera Cycloryx and Raptomphalus were described by Godwin-Austen (1914). The former is characterised by the ovate-conoid shell and an extremely short tube, which is often pear or clubshaped, whereas the latter has a conspicuous keel on the umbilical margin. Stomacosmethis Bollinger, 1918 was defined on the basis of a pipe, tongue or cup-shaped structure on the outer side of the operculum and included two species from southern Celebes and eastern Borneo. Three genus-group taxa (Sigmacharax Kuroda, 1943, Cipangocharax Kuroda, 1943, Awalycaeus Kuroda, 1951 were described from Japan. These have been used either as genera or as subgenera of Chamalycaeus and can be distinguished from each other as follows: Sigmacharax has a peculiar, sigmoid last whorl with an ovate aperture having an interior ridge, Cipangocharax has a thick, "shelly" operculum with closely imbedded spiral cuticular lamellae on its outer surface, and Awalycaeus has a very short distance between the starting point of the tube and the peristome, its operculum is situated at the aperture, not deeper as in other groups. In our own works we have defined Metalycaeus by the presence of a spirally striated protoconch, and several species from China, Vietnam, Laos, and Japan have been placed in this genus . We also found that Chamalycaeus possesses a protoconch without spiral striae, and a teleoconch with spiral striation. Consequently, most species previously classified as Chamalycaeus have been transferred to Metalycaeus or Dicharax. The latter is characterised by the absence of spiral striation on the entire shell . We further synonymised Cycloryx with Pincerna, which is accepted as a distinct genus (Páll-Gergely 2017).

Materials and methods
Specimens (shells and radulae) were examined using a low vacuum SEM (Miniscope TM-1000, Hitachi High-Technologies, Tokyo) directly without coating. The ethanolpreserved specimens were dissected under a Zeiss stereomicroscope, and photographs were taken using a Keyence LHX5000 digital microscope.
Photographs of shells were taken using various photographic equipment in our laboratories and in museum collections. Photographs of types deposited in the IZCAS, ZSI, SMF are published here. In cases of the other museums the photographs of types are mostly available online, or they will be published by us in separate papers.
Locality data cited as verbatim from the specimen labels, and no English translations are provided in most cases.
Differences in size are indicated in the generic diagnosis using the following terms: very small (smaller than 3 mm), small (3-4 mm), medium-sized (4-6 mm), large (6-8 mm), very large (larger than 8 mm). We distinguish three regions of the teleoconch, following : Region 1 (R1) ranging from the beginning of the teleoconch to the beginning of the differently ribbed region where the sutural tube lies, Region 2 (R2) extending from the end of R1 to the constriction (i.e., the length of R2 usually corresponds with the length of the sutural tube, see Páll-Gergely et al. 2016; Páll-Gergely and Asami 2017), and Region 3 (R3) ranging from the constriction up to the peristome.
In order to maintain consistency with the editorial conventions of MolluscaBase (2020), initials of first names of authors are indicated in all cases where a given author shares the same family name with another malacologist (i.e., Y. Hirase, L. Pfeiffer).

R1 sculpture
Spiral striation is absent only in Dicharax. All the other genera possess some spiral striae of varying development. These spiral striae consist of microscopic elevated ridges arranged in clearly visible spiral lines. Some spiral striae visible in a few Dicharax species (e.g., D. candrakirana, D. depressus), however, is appear to be a part of the inner shell layers and may not be homologous with those of Chamalycaeus and Metalycaeus.
The strength of radial ribbing is also informative (usually strong in Chamalycaeus and Pincerna, weak in Alycaeus and Stomacosmethis). Dioryx has overall weak sculpture, whereas it is highly variable in Metalycaeus.

Length of R2
Stomacosmethis is characterised by very short R1 (with a short, tumid, sometimes pearshaped tube), whereas Alycaeus possesses very long R1 (ca. 0.5 whorl). Most Pincerna species, especially the ones classified in Cycloryx previously, possess a short tube, but some species have a longer tube than usual for that genus. Distinction between longertubed Pincerna and Alycaeus is the most problematic part of the current classification. The remaining genera (Chamalycaeus, Dicharax, Dioryx, Metalycaeus) exhibit high variability in terms of the tube length.

Sculpture of R2
Highly variable within each genus with the exception of Dioryx, which has no elevated R2 ribs. Typically, Chamalycaeus and Metalycaeus species possess widely spaced, sharp ribs. However, Metalycaeus vinctus has widely spaced, sharp ribs, but its putative sister species M. minatoi has a smooth outer surface in R2 without any elevated ribs. This seems to indicate that this trait may differ substantially even between closely related species. Similar examples are found among some Himalayan Metalycaeus species, and also among the Chinese Dicharax moellendorffi vs. other Dicharax species. Typical Dicharax species possess R2 ribs that curve towards the aperture.  Fulton, 1902 (HNHM 99714, spec3). Scale bars: 1 mm. All images: Barna Páll-Gergely. Metalycaeus minatoi Páll-Gergely, 2017: ovarium slender, pointed anteriorly and rounded posteriorly, bursa copulatrix, rounded, does not extend beyond ovarium, opens near opening of ovarium, receptaculum seminis small, rounded (Fig. 3J, K). Stomacosmethis dohrni (O. Boettger, 1893): shape of ovarium could not be examined due to its decayed condition, but it is probably oval, bursa copulatrix large, elongate, strongly extends beyond ovarium posteriorly, opens at centre of ovarium, receptaculum seminis small, oval (Fig. 3L, M). Stomacosmethis balingensis (Tomlin, 1948): ovarium peanut-shaped, bursa copulatrix was damaged, its posterior part could not be dissected out, opens at anterior part of ovarium, near ovarium opening, receptaculum seminis elongated, a complicated spermoviduct was found in bursa copulatrix: its head is pointed drop-shaped, both ends of the head connected to a slender stalk that forms a flattened loop, the entire length of the stalk is continuous, forming a ring (Fig. 3N, O).
Our knowledge of genital anatomy of terrestrial operculate snails is far more limited than that of pulmonates, probably because dissection of the soft body is more difficult. Firstly, the reproductive organs are not so clearly separated as in pulmonates, but are attached to neighbouring tissues and organs. Secondly, tissues of ethanol-preserved animals are far more fragile. Therefore, it is much more difficult to see the boundaries and junctions of certain organs. For the current study much of the ethanol-preserved material was not in a suitable condition for reproductive anatomy. More than half of the available material was not used for this reason.
So far, the reproductive anatomy of the Alycaeidae is little known. Tielecke (1940) published a few notes without figures on two alycaeid taxa. Although we have dissected a few female specimens, our observations of reproductive anatomy are insufficient to feed into our classification between genera. Considerable differences could be observed in the relative size of the bursa copulatrix, thickness and origin of the bursa's stalk, shape of the bursa and receptaculum seminis. The taxonomic value of these traits must be clarified by further observations. Nevertheless, the bursa copulatrix originates from the lateral side of the ovarium, which may probably be a synapomorphic character of the Alycaeidae. In contrast, the bursa starts from the terminal (distal) end of the ovarium in all the anatomically examined specimens of Cyclophoridae (Tielecke 1940).
by Venmans (1956). It is highly likely that Venmans mixed the radular drawings or radulae of those two species. Therefore, in our analysis of alycaeid radulae we ignore the data of Venmans (1956).
The radula morphology of 28 species are known from the available literature and this study (excluding the results of Venmans 1956). In every species the radular teeth are arranged in v-shaped rows, each transverse row with seven teeth (2-1-1-1-2). The central tooth is strongly constricted in its middle part. The lateral and two marginal teeth have slighter median constriction of the plates and are seemingly longer and slenderer than the central tooth, except for Stomacosmethis, where they are of comparable width to the central teeth. The lateral and marginal teeth are similar in terms of shape of the cusps to the central teeth in all examined specimens.
There are generally two types of central teeth. One type has one round tooth with 5-7 cusps, and the other is elongated with 1-5 (usually 1-3) cusps. The former type is Table 1. Radula traits of Alycaeidae. For the species examined by Venmans (1956) see Radula under "Description and assessment of morphological characters" (page 14).  Chen 1989 common among all the genera (Alycaeus, Chamalycaeus, Dicharax, Dioryx, Metalycaeus, Pincerna), whereas the latter, elongated type has only been observed in Stomacosmethis species. The placement of S. balingensis in Stomacosmethis is mainly based on its radular morphology, which is similar to that of sympatric S. perakensis. The first type of central teeth can be further subdivided into groups with a blunt (Alycaeus, Dioryx) or pointed (Chamalycaeus, Dicharax, Metalycaeus, Pincerna) central cusp. However, a Chamalycaeus species we examined had a blunt central cusp. The type with a pointed central cusp is a probably plesiomorphic character, which is visible in many terrestrial caenogastropods (e.g., Cyclophorus, Cyclotus, Japonia, see Egorov 2009). Together with conchological, anatomical and molecular phylogenetic information the radular traits may provide insights about relationships of alycaeid genera (see Concluding remarks).

Genus-level diversity
Of the 14 nominal genus-group taxa that have been described (Table 2), we accept seven.
The classification proposed in this study is based on unique character states (Dicharax, Dioryx, Metalycaeus) and on unique combinations of character states (other genera) ( Table 3). The number of accepted species-level taxa is: Alycaeus: 7,Chamalycaeus: 26,Dicharax: 164,Dioryx: 30,Metalycaeus: 61,Pincerna: 37,Stomacosmethis: 37. Besides taxonomic problems at the species level (see under Annotated list of species group taxa), some aspects of grouping species into genera turned out to be especially challenging. As a result, the generic boundaries are not completely clear. This may be due to repeated evolution of morphological traits and the presence of the large Table 2. Genus-group taxa of the Alycaeidae. Abbreviations: M: monotypy, OD: original designation, SD: subsequent designation. Valid genera are marked with an asterisk.  Kuroda, 1943 Chamalycaeus (Sigmacharax) itonis Kuroda, 1943 M synonym of Dicharax *Stomacosmethis Bollinger, 1918 Alycaeus (Stomacosmethis) sarasinorum Bollinger, 1918 SD accepted numbers of species in the genera. In the absence of phylogenetic analyses, the current classification is tentative. We anticipate that some adjustments are inevitable as our understanding of the evolutionary history of this family improves. Some remarks about the species boundaries (numbers correspond with Fig. 5): (1) Metalycaeus is characterised by the presence of spirally striated protoconch. However, in rare cases the striation is strongly reduced (see M. laevis).
(2) Dicharax is characterised by the absence of spiral striation on both the protoconch and teleoconch. However, striation is present in a few Dicharax species (see remarks under D. candrakirana, and D. depressus). Striae are not elevated threads but are probably a part of the inner shell layers; this structure would not be homologous with the striae present in the other genera. Dicharax is a diverse genus containing 166 species and subspecies. However, meaningful subdivision is not possible at present. (3) Dioryx and Alycaeus are clearly separated based on the presence of R3, globular shape and weak sculpture of Dioryx. Although the R3 in Alycaeus conformis renders its shell somewhat similar to the shell of Dioryx species, we consider Dioryx to be a recognisable group, which would be monophyletic. (4) Distinction between Alycaeus and Pincerna is probably the most problematic issue in the system presented here. The genus Cycloryx (treated as a synonym of Pincerna) originally contained species with a very small shell, which has elevated spire usually with strong ribs and very short tube, and taxa from the Himalaya region and northern Myanmar. However, similar species are disjunctly found from Sumatra (Pincerna yanseni), northern Vietnam (A. costulosus) and Borneo (A. globosus). For example, the shell of P. yanseni is hardly distinguishable from that of Hymalayan  (5) Chamalycaeus species have a depressed shell with reticulated sculpture and a sutural tube and R2 which vary in length. Pincerna species have higher spire, sculpture dominated by radial ribs and sometimes a short tutural tube. Pincerna crenilabris seemingly connect the two genera by its rather globular shell and medium-sized tube. (6) The genus Stomacosmethis is characterised by colorful triangular shell mostly with flat whorls and a very short tube. Pincerna species from the distributional range of Stomacosmethis differ by having round whorls and a short tube. All Stomacosmethis species that were examined for radular traits possess unique, simple teeth (Fig. 4H, I). However, a similar type of radula has been found in A. balingensis, which could be classified as Pincerna based on the shell shape (round whorls). For this reason, A. balingensis is here moved to Stomacosmethis. This example suggests that Pincerna and Stomacosmethis might not be mutually monophyletic. Further examinations are necessary to verify the generic position of Pincerna species. (7) One of the most important results of this study is discovery of distinct differences between Alycaeus and Stomacosmethis, which form two groups without taxa that exhibit overlapping traits of morphology.

Annotated list of species-group taxa
In this study we list 412 species-group names including eleven replacement names (seven of them proposed in this study) and five nomina nuda (Table 4). Types of 336 species and subspecies (85%) were examined, and of 19 taxa non-type specimens were examined (5%), whilst we relied on the sufficiently detailed original descriptions of the 22 taxa (6%). For 17 taxa (4%) no material was available to be examined in this study. Of the 395 taxa, 32 are considered synonyms, although no recent revision has been undertaken for some more specific geographic areas, such as the Himalaya region. Consequently, 362 species-group taxa (320 species and 43 subspecies) of the Alycaeidae are currently accepted. Twenty-two were described by us in previous publications, and there are 18 species, that were formerly classified in Cycloryx that now belong to Pincerna due to its synonymy with Cycloryx. Of the 323 remaining species (excluding our taxa and Cycloryx), 209 (65%) are here classified in a new genus, whilst 114 (35%) remain in their previously classified genus. Most of these changes in generic placement resulted from two reasons. Firstly, morphological traits for generic definitions in the preceding studies were not able to classify the currently recognised taxa in morphologically distinct groups, and thus, probably the genera did not reflect evolutionary relationships. Secondly, the type species of each genus were not examined adequately before assigning a new species in these genera.
Alycaeids possess complex shell morphology compared to many other land snail groups, and exhibit a considerable magnitude of variation between populations, which could be interpreted as intraspecific or interspecific variation. Thus, a lumping approach would recognize much fewer taxa than a splitting approach. We employed the former approach, which would be most appropriate when examining widespread and variable taxa such as Dicharax cristatus, D. fimbriatus or Metalycaeus muciferus (see ). This would be most practical for systematic handling of enormous morphological variability among the currently available specimens in the Alycaeidae. The 'splitting' approach to these groups would have resulted in recognition of twice as many or even more species. For example, Foon and Liew (2017) have described several species from Peninsular Malaysia based on small quantitative differences in shell sculpture and size, which would be appropriate for subspecific distinction. Although the present study did not include revision of northeastern Indian Alycaeidae, we found that some of Godwin-Austen's species exhibit rather minor differences (M. brahma and its two new synonyms, and D. birugosus, and its new synonym, D. canaliculus are examples). Accordingly, geographic variation of the currently recognized alycaeid species diversity largely stem from difference between the splitting and lumping approaches employed by the authors. Diagnosis. Shell with a complex gas exchange system consisting of a common external sutural tube and several extremely narrow, perpendicularly running microtunnels, formed by the outermost shell layer (Páll-Gergely et al. 2016). Bursa copulatrix connecting to lateral side of ovarium.
Remarks. In the past this group has been treated as a subfamily of the Cyclophoridae, and as a family of its own right. The complex gas exchange system, combined with the unique position of the bursa copulatrix (both are important synapomorphic characters), seems to justify the distinction of this group as an independent family.
Diagnosis. Shell very large (D: 8-15 mm), triangular, with body whorl being dominant due to very long R2; protoconch smooth, obliquely striated, or transitional character state of the two; R1 usually finely reticulated, due to fine radial ribs and fine spiral striation; R2 long or very long (usually almost reaching 0.5 whorl), smooth or with lamella-like, straight, dense ribs; umbilicus narrow. Operculum thin or relatively thickened (can have both calcareous and proteinaceous layers, Foon and Liew 2017), without elevated outer structure (although scaffold-like calcareous structure and ap-pressed radially spiral lamellae can be present, see Foon and Liew 2017). Central tooth with five cusps, broad, central cusp blunt.
Differential diagnosis. The sculpture of Alycaeus and Chamalycaeus (smooth protoconch, spirally striated, weakly ribbed teleoconch) are identical, although Chamalycaeus tend to have stronger ribs. The distinction is based on the narrow (Alycaeus) and wide (Chamalycaeus) umbilicus. Furthermore, Alycaeus shells are larger, more colourful (reddish or yellowish) and the very long (i.e., ca. 0.5 whorl-long) R2 in Chamalycaeus is very rare.
Typical Pincerna has a relatively short tube and a strongly ribbed teleoconch, whereas typical Alycaeus possesses a long tube and its teleoconch is weakly ribbed. Some species (P. anceyi, P. mouhoti) form connections between the two genera. However, we prefer to maintain the distinction between Pincerna and Alycaeus due to the many species characteristic to both respective genera.
Alycaeus is easily distinguished differs from Stomacosmethis which has a yellowishorange, triangular shell, and a very short tube.
Distribution. This genus is known from northern Laos and northern Vietnam until the southern end of the Malay Peninsula (Fig. 7).
Remarks. Regarding the authorsip of Alycaeus (i.e., Baird vs. Gray), we follow Petit (2012: 24-25).  Remarks. Protoconch with oblique ribs; R1 densely, finely, regularly ribbed with some very weak spiral striation; R2 very long, with dark and light stripes, the lighter being slightly narrower and more elevated from the surface.

Alycaeus conformis Fulton, 1902
Alycaeus conformis and A. gibbosulus have a characteristic, oblique striation on the protoconch (Fig. 2). However, the protoconch of A. rolfbrandti is also strongly sculptured (mamillated), and at the end of the protoconch oblique striae can be seen. Therefore, there is a continuous transition from the smooth Alycaeus-type protoconch sculpture to that of A. conformis and A. gibbosulus. Due to the similarity in protoconch sculpture and the geographic proximity (they are also found in mixed museum samples), A. conformis and A. gibbosulus are presumably closely related.  Type locality. "que dans les grottes formées dans l'intérieur des montagnes de marbre qui s'élèvent au milieu de la plaine oú est bâtie la ville de Turanne, en Cochinchine".
Remarks. Protoconch matte, without spiral lines; R1 fine, dense, rather regular ribs with weak spiral striation; R2 long, with dense, lamellae-like, elevated ribs, which are most elevated closer to the suture. Below the ribs, the microtunnels are visible as narrow light bands between the darker, thicker stripes (visible where there are weathered areas of the shell). Habe (1965) reported "Dioryx gibbus (Reeve)" from "Kao Phlong, north or Sara Buri, Central Thailand", without publishing a picture. This almost certainly refers to a different species.

Alycaeus jousseaumei de Morgan, 1885
Alycaeus jousseaumei de Morgan, 1885b: 402, pl. 8, fig. 4  Remarks. Spire low, but upper whorls (not only the protoconch) elevated; Protoconch glossy, R1 with very weak, irregular growth lines and even weaker, fine spiral striation; R2 very long, with wider darker stripes and lighter, narrower channels between, the channels are somewhat elevated from the surface. Remarks. The two syntypes in the NHM and one of the shells from Cambridge were weathered. The third shell from Cambridge is in a good state, and its sculpture could be examined. Protoconch without particular sculpture, rather matte; R1 with low, irregular growth ridges; R2 relatively short, but much longer than typical in Stomacosmethis, the surface is irregularly wrinkled, and possibly ribbed near the suture. Habe's (1965) record of this species from "Khao Chong, Trang Province, peninsular Thailand" refers to Alycaeus gibbosulus.  Remarks. Protoconch irregularly ribbed, squamous, the last ca. 0.25 whorl with oblique ribs similar to those of A. conformis and A. gibbosulus; R1 with regular, fine, low ribs without spiral striae; R2 long with dense, lamella-like ribs (very similar to those of A. eydouxi).

Alycaeus rolfbrandti Maassen, 2006
The shells in the Senckenberg Museum are part of the original series of the species collected by Brandt, but since Maassen did not state that he examined them, they are not part of the type series.
Remarks. We were unable to examine shells of Alycaeus somwangi, but the original description provides enough information to allow for generic placement. Protoconch without spiral striae, R2 very long, with regular, low ribs.

Genus Chamalycaeus Möllendorff, 1897
Alycaeus ( Type species. Alycaeus (Chamalycaeus) fruhstorferi ( Fig. 6B) by monotypy, see also Remarks. Diagnosis. Shell very small to medium sized (D: 2-5 mm), usually flattened, discoid or low triangular, protoconch smooth (or very finely pitted), elevated even if the spire is low; R1 usually roughly reticulated due to spiral striation and radial ribs (sometimes prominent); R2 from short to very long, with widely spaced, sharp, elevated ribs; R3 normally developed. Operculum usually thin, without notable outer structures. Radula is known for a single species (central tooth with five cusps, broad, central cusp pointed).
Differential diagnosis. See under Alycaeus and Table 3. Metalycaeus species are identical, with the exception of the spirally striated protoconch.
Distribution. Chamalycaeus is distributed from the southeastern Himalaya Region, the Malay Peninsula, Sumatra, Java, Borneo, Sulawesi, and the Philippine Palawan Island (Fig. 9).
Remarks. Kobelt and Möllendorff (1897) listed the species of "Pneumonopoma", which included all members of the genus Alycaeus. They introduced "Subgenus Chamalycaeus n." (Kobelt and Möllendorff 1897: 148), indicating it as a new subgenus, and included 44 species within their new group. The subgenus Chamalycaeus, however, was previously mentioned in another paper in the same volume of the Nachrichtsblatt der Deutschen Malakozoologischen Gesellschaft, in which Möllendorff (1897b: 93) described Alycaeus (Chamalycaeus) fruhstorferi. Möllendorff's (1897b) paper was published in July-August, whereas that of Kobelt and Möllendorff (1897) was published in September-October. Accordingly, the genus Chamalycaeus was described by Möllendorff (1897) and its type species is Alycaeus (Chamalycaeus) fruhstorferi by monotypy. On the other hand, Alycaeus (Chamalycaeus) fruhstorferi was not listed in Kobelt's and Möllendorff's (1897) paper, which indicates that they aimed to describe A. fruhstorferi after their revision of Alycaeus. Moreover, Kobelt's (1902) monograph referred to Chamalycaeus as it was introduced by Kobelt and Möllendorff (1897). Almost all subsequent treatments erroneously attributed the name Chamalycaeus to Kobelt & Möllendorff, 1897(Kobelt 1902Gude 1921;Yen 1939;Zilch 1957;Azuma 1980;Minato 1982bMinato , 1987aMinato , 2005Minato and Yano 1988;Egorov 2005;Zhang et al. 2008) and referred to Alycaeus andamaniae Benson, 1861 as the type species as subsequent designated by Gude (1921). The ICZN Code 70.2 states the following: "If it is found that an earlier type species fixation has been overlooked, the overlooked fixation is to be accepted and any later fixations are invalid. If this is considered to cause instability or confusion the case is to be referred to the Commission for a ruling". Therefore, we must examine whether the correction of the type fixation would cause instability. In our view, confusion or instability would be caused only if the majority of authors who have described species within Chamalycaeus were unaware of the shell morphology of Alycaeus andamaniae (incorrectly selected as the type species for Chamalycaeus). No detailed description of Alycaeus andamaniae has ever been published, and our revision suggests that most authors who described Chamalycaeus species did not examine samples of Alycaeus andamaniae. Thus, we find no reason to present this issue to the Commission. Instead, we follow Egorov (2013) in accepting Möllendorff (1897b)  Remarks. Protoconch low, no spiral striation visible. The specimen largely matches Benson's original description, and therefore we consider it to be the holotype. The photographs of that specimen show some signs of spiral striation. However, those striae may be part of the lower shell layers, and not raised threads as in other Chamalycaeus species. Consequently, the spiral striae on the holotype of A. armillatus may not be homologous with the ones in Chamalycaeus species; we would need fresh shells to confirm this. For the time being, we refer to this species as Chamalycaeus (?) armillatus.

Remarks.
Protoconch elevated, no spiral lines visible, although the suture is filled with dirt and the photographs are not of high quality. R1 with strong widely spaced, ribs with a fine spiral striation; R2 with denser, straighter ribs, although this part of the shell was somewhat corroded. This species is placed in Chamalycaeus due to the colourless shell and biogeographic location. A closer examination of the protoconch would be important to rule out its affinity with Metalycaeus, although the occurrence of that genus in Celebes would be surprising. Remarks. Aldrich (1889) did not give a name for the "Alycaeus sp.", species he figured and described, because he thought it might be A. spiracellum, which he was unable examine for comparison. He mentioned that "if new, I propose the name Alycaeus broti for it". This action does not make the name available, because under ICZN Art. 11.5 "To be available, a name must be used as valid for a taxon when proposed", which was not the case for A. broti; therefore, the name Alycaeus broti is not available. Smith (1895) mentioned that he compared A. everetti specimens with his "A. broti", and they were identical.

Chamalycaeus everetti (Godwin-Austen, 1889)
Protoconch elevated, no spiral lines visible; R1 with very fine, irregular ribs and spiral lines; R2 short, with sharp, straight, widely spaced ribs. ( Remarks. Protoconch elevated without spiral lines; R1 with weak, widely spaced, irregular ribs and somewhat stronger spiral striation; R2 relatively short, with widely spaced, elevated, sharp ribs. Remarks. Protoconch elevated, no spiral lines visible; R1 rather regularly ribbed with sharp ribs, and with somewhat weaker spiral striation; R2 relatively long, with widely spaced, sharp ribs. Remarks. The examined paratype was badly weathered, only the elevated protoconch with some spiral lines on R1 and the short tube were visible. Based on these, C. kessneri remains classified in the genus Chamalycaeus.

Chamalycaeus kessneri Vermeulen, 1996
The shells from Nateh were considerably smaller than typical C. kessneri, but agreed with that species in terms of shell shape, the short tube, and the spiral striation. Although these six shells were also weathered, one of them was in a relatively good condition. None of the shells showed signs of spiral striation on the protoconch, therefore the placement of this species in Chamalycaeus seems to be justified. Diagnosis. Protoconch rather low, without obvious spiral lines, the granules following a near spiralling arrangement, but not at all similar to the multiple, narrow spiral striae typical to most Metalycaeus species; R1 with rather regular ribs and strong spiral lines; R2 extremely short, with only ca. five ribs which are blunt (probably bent?). Operculum unknown.   (Möllendorff, 1887), lectotype (SMF 109493) B C. mixtus Zilch, 1957, holotype (SMF 109510). All images: Barna Páll-Gergely, courtesy Ronald Janssen.
Remarks. Protoconch as in C. microconus; R1 with rather irregular, widely spaced, low ribs, with somewhat stronger spiral striae; R2 extremely short, consists of ca. eight ribs which are bent in the direction of their anterior neighbours. Remarks. Protoconch elevated, no spiral lines visible; R1 with rather irregular, low ribs, and weaker spiral striation; R2 very long with widely spaced, sharp ribs. Remarks. Protoconch elevated, no spiral lines visible; R1 irregularly, weakly wrinkled and as strongly spirally striated; R2 moderately long, with wider darker and narrower lighter stripes alternating, the overall surface is nearly smooth, rather irregularly wavy.
Material examined. Only the holotype (UF 525657) is known.
The placement of this species into the genus Chamalycaeus is based on biogeographic information alone, since the protoconch, which is necessary for generic allocation, is absent in the only available shell (Páll-Gergely and Auffenberg 2019).
The original spelling of the species was reinhardi, which was corrected to reinhardti by Kobelt (1902). This was a justified emendation under the Article 32.5. of the ICZN Code, because it was obvious that Mörch (1872a) named the new species after the collector Reinhardt.
Godwin-Austen (1895) mentioned that the type of this species is from Great Nicobar Island, and the form from Camorta is named f. minor by Mörch. However, we have not found the publication in which Mörch introduced that name.
Reeve's A. nicobaricus was not examined by us, but it was considered to be a junior synonym of A. reinhardti by Gude (1921).

Remarks.
Spire elevated, shell slightly wider than high; protoconch elevated, no spiral lines visible; R1 with irregular ribs, and somewhat weaker spiral lines; R2 relatively long, with widely spaced, regular, sharp ribs.

Chamalycaeus reticulatus (Möllendorff, 1897)
Alycaeus ( Remarks. The original description does not mention the number of examined specimens. Thus, we consider the specimen labelled holotype (SMF 57196) as a syntype.

Alycaeus sculptilis
Remarks. Protoconch elevated, no spiral lines visible; R1 with rather regular, widely spaced ribs, and somewhat weaker spiral lines; R2 long, with widely spaced ribs; there is a lamella on each rib which is slightly bent in the direction of the anterior neighbour.
Remarks. The syntype is weathered and was glued to a piece of black paper by its R2 area, therefore limited information could be gained during its examination. The shell is depressed and conical; protoconch strongly weathered, but there were no signs of spiral striation near the suture; R1 regularly and strongly ribbed with very weak spiral striation; length of R2 could not be fully seen, but has low, dense riblets and fine spiral lines. We received photographs and good quality drawings of newly collected shells from Thor-Seng Liew and Jaap Vermeulen (pers. comm. August 2019), and those confirmed that this species is a Chamalycaeus due to the colourless shell, long R2, and relatively strong ribs. Remarks. Protoconch elevated, finely pitted, no spiral lines visible; R1 with dense riblets and some weak spiral striation; R2 short, with somewhat elevated ribs that are similar to those on R1.

Chamalycaeus sumatranus (E. von Martens, 1900)
Remarks. The original description does not mention the number of examined specimens. Thus, we consider the specimen labelled holotype (ZMB/MOLL, 51748) as a syntype.
Protoconch elevated, no spiral striation visible; R1 with rather irregular, low ribs and spiral striation roughly of the same strength; R2 long, with widely spaced, sharp ribs.
Type locality. "Munipur. Exact locality not recorded; somewhere on the northern side of the valley".
The absence of spiral striation on the entire shell is unusual for Chamalycaeus, and characteristic for Dicharax. However, the general shell shape, the strong, equidistant ribs, and the elevated protoconch suggests that this species belongs to Chamalycaeus.
Differential diagnosis. This genus can be recognised by the absence of spiral striation on the entire shell (protoconch and teleoconch). Very few species with spiral striation are classified in this genus.
Distribution. Dicharax inhabits a large geographic area from the southeastern Himalayan region to Japan, and through the Malay Peninsula to the southern arc of the Malay Archipelago up to Sumatra and Java. There are also isolated occurrences in the Western Ghats of India and in the southwestern Himalaya (see Fig. 14).
Remarks. Cipangocharax, introduced as the subgenus of Chamalycaeus, was described for a single species, Alycaeus biexcisus. The diagnosis of Cipangocharax was in fact the abbreviated description of Alycaeus biexcisus. Kuroda (1943) indicated some features in italics, emphasising the importance of these characters to distinguish Cipangocharax from other members of Chamalycaeus. These characters were the extraordinary thickness of the operculum, and the closely coiled outer belt on the outer surface of the operculum. The Japanese Chamalycaeus species described since Kuroda's (1943) paper showed that there are transitional character states between the thick and belted operculum of A. biexcisus and the thin and unbelted opercula of most Japanese Chamalycaeus species (e.g., Minato 1993). For example, the operculum of Cipangocharax kiuchii is relatively slim, whereas that of "Chamalycaeus" miyazakii is exceptionally thickened. Consequently, the thickness of the operculum is not a distinguishing feature between Cipangocharax and other Japanese species assigned to Chamalycaeus. The outer opercular belt is missing in C. placenovitas (a species being otherwise very similar to A. biexcisus), therefore this character is also not stable within the genus. Moreover, the outer belt is known to be present and absent within the same species, or even population (see under Chamalycaeus nipponensis and Dicharax simplicilabris, see . The other distinctive character mentioned by Kuroda (1943) is the sinuated columellar margin. This region is not sinuated either in C. placenovitas, or in C. okamurai. Therefore, this character is also not stable within the genus. Moreover, Japanese Chamalycaeus species with unstriated protoconchs show an extraordinary diversity in terms of the formation of the aperture (C. expanstoma, C. okamurai, C. yanoshigehumii), indicating that the morphological variation is very high between species. Consequently, among the Japanese species with unstriated protoconch, it would not be legitimate to classify certain species into separate (sub)genera from the others. Furthermore, the species classified into the genus Sigmacharax also do not differ considerably from the rest of Japanese species with a smooth protoconch. Therefore, based on the absence of the spiral striation on the entire shell, these species are classified in the genus Dicharax. The overlapping ribs near the tube (Fig. 15) may a synapomorphic character of Japanese and Korean Dicharax, but this character was also found in the Chinese species D. alticola , which is, due to the geographic distance, probably only distantly related. The morphological variation within the genus Dicharax (especially in northeastern India and in the Malay Archipelago) is so large, that at the current time we do not find it meaningful to separate the Japanese and Korean species into a separate subgenus within Dicharax.
Such 'over spitting' of generic taxa inhabiting Japan has also been documented in the pulmonate family Clausiliidae, which is a character-rich family such as the Alycaeidae (Páll-Gergely et al. 2019). Nordsieck (1998) stated that the Japanese clausiliid genera and subgenera correspond only to subgenera and species groups of Western Palaearctic clausiliids. This claim was confirmed by recent molecular phylogeny (Motochin et al. 2017).
For the sake of simplicity, this genus is divided into three sections: typical (with curved R2 ribs), atypical (without the typical R2 sculpture), and those species from Japanese and Korean localities (including species formerly classified into Awalycaeus, Cipangocharax, and Sigmacharax). Protoconch low, glossy, without spiral lines; R1 rather regularly ribbed, ribs low, no spiral striation visible; R2 relatively long, with ribs curved towards the aperture, forming a smooth surface. Remarks. Syntypes: protoconch low, spiral lines not visible; R1 irregularly ribbed, without spiral lines; R2 moderately long, with lamella-like, straight ribs.

Dicharax asaluensis
Other sample. The specimens are conspicuously variable in term of shell size (smallest: D = 2.7 mm, H = 2.1 mm; largest shell: D = 4.0 mm, H = 2.9 mm), the sculpture of R1 (nearly smooth to strongly, regularly ribbed) and the sculpture of R2. Despite the large variability, we consider all shells to belong to the same species since the variation is continuous between the extreme morphological forms. Protoconch low without spiral striation. R2 of some specimens typical Dicharax-like (ribs are curved towards the aperture), whereas those of other specimens are more lamella-like and less curved. Note that the shells with straight, lamella-like ribs on R2 are not weathered, which demonstrates that the two types of ribbing are a part of the intraspecific variation. Type locality. "The hills east of Mandalay and Ava".
Remarks. Protoconch low without spiral lines; R1 irregularly, densely ribbed, no spiral lines visible; R2 relatively short; ribs lamella-like, curved towards the aperture, but they are not in contact.
Remarks. Protoconch rather glossy, low, no spiral lines visible; R1 glossy, with widely spaced sharp ribs which are present only near the suture, and without spiral lines; R2 with curved ribs, typical to Dicharax.
The only stable character which distinguishes D. chennelli from D. diagonius is the presence of a lower apertural bay in the former, whilst it is absent in the latter.
Remarks. Protoconch low, no spiral lines visible; R1 is similar to protoconch by being moderately glossy and sculptureless; R2 short, with regular ribs curved towards the aperture, forming a relatively wide, flat area, when viewed from above.  (2 syntypes). Note that the type locality does not match with the locality of the type sample, but the type locality was clarified in Godwin-Austen 1914in 1897, and the drawing in the original description is identical with the two syntypes.

Dicharax conicus jatingaensis
Remarks. Protoconch rather glossy, low, without spiral lines; R1 rather regularly, finely ribbed without spiral striation; R2 relatively short, with regular ribs curved towards the aperture. Remarks. Protoconch moderately glossy, low, no spiral lines visible; R1 with regular ribs and without spiral striae; R2 is moderately long, the upper part of the ribs are horizontal (in cross-sectional view the ribs are T-shaped); in most cases the ribs do not reach each other.
Remarks. Protoconch low, glossy, very finely granulated, no spiral lines visible; R1 finely, regularly ribbed without spiral lines; R2 long, with strong signs of Byne's disease; the ribs are curved towards the aperture and reach each other (typical Dicharax structure), forming a glossy, nearly smooth surface.
Remarks. Protoconch low, rather matte, without spiral lines; R1 with similar sculpture to that of the protoconch; R2 very short, with ca. 20 regular ribs, ribs curved towards the aperture. Remarks. Protoconch low, rather glossy; R1 with low, regular ribs, ribbing weaker at beginning of R1, but stronger at end of R1; R2 with ribs curved towards aperture. Material examined. Cheng-Kou County, Chong-qing, China, HMT-218a, deposited in IZCAS (syntype: labelled as lectotype, but probably there was no valid lectotype designation). No type specimens deposited in American museums were reported by Johnson (1973).
Remarks. This species could be examined for the first time, since it was not examined in our previous paper . Protoconch low, smooth; R1 without spiral striation, its beginning is densely, finely ribbed, which gradually changes to a more widely-spaced, strongly ribbed surface. R2 and R3 are of comparable length, R2 ribs dense, low, blunt, not elevated. The most similar species is D. fargesianus, which has denser ribs on R1 and R3, and more marked swelling on R3.
The examined specimen has a shorter R3 than the one illustrated by Heude (1890) (see also Páll-Gergely et al. 2017: fig. 69I). This raises some doubts about the identity of this type.

Dicharax generosus (Godwin-Austen, 1914)
Alycaeus generosus Godwin-Austen, 1914: 374, pl. 138 Remarks. Protoconch low, glossy, no spiral lines visible; R1 with low, irregular growth ridges, but otherwise glossy without spiral lines; R2 moderately long, with regular ribs nearly reaching each other; the ribs near the beginning of R2 are bent in an anterior direction, the ribs near the end of R2 are bent in a posterior direction, and the ribs in the middle section of R2 are T-shaped in cross sectional view. Remarks. The only available specimen housed in the NHM was weathered; Protoconch low, with any recognisable sculpture; R1 with irregular, fine ribbing which turns into a widely spaced, strongly ribbed area at the end of the region, no spiral lines visible; R2 relatively short, weathered. SMF sample: protoconch low, rather glossy; R1 also glossy, with widely spaced, strongly ribs near the end of the region, no spiral lines visible; R2 relatively short, ribs curved towards the aperture. Remarks. Protoconch without any recognisable sculpture, although it was weathered in examined shells; R1 smooth, glossy, with sharp, widely spaced, regular ribs near suture and inside umbilicus; R2 finely, densely ribbed, ribs are curved towards aperture at end of R2, but in curved in posterior direction at beginning of R2.

Remarks.
Protoconch matte, R1 smooth, no spiral lines visible (although the entire shell is somewhat weathered); R2 of normal length, the ribs are overall low, they are slightly curved towards the aperture.

Dicharax kezamaensis (Godwin-Austen, 1914)
Alycaeus kezamaensis Godwin-Austen, 1914: 393, pl. 149, fig. 1 Remarks. Protoconch low, glossy, no spiral lines visible; R1 glossy, with some spiral lines, which are, however, not present on the surface but are found on parts of the inner layers of the shell and visible through the semi-transparent upper layer (thus, not homologous with the spiral striation of other genera); R2 short, with lamella-like, sharp ribs, which are slightly curved towards the aperture; there is quite large gap between the ribs. Remarks. Protoconch low, no spiral lines visible; R1 rather regularly, finely ribbed without spiral lines; R2 very long, with regular ribs, which are curved towards the aperture, and reach each other (typical Dicharax).
Type locality. "Khasi Hills, near Cherrapunji, at the mouth of the Maosmai cave".
Remarks. Protoconch low, rather matte, no spiral lines visible; R1 with very widely spaced wrinkles without spiral striation; R2 moderately long, the ribs are bent and do not reach each other (typical Dicharax structure).
Remarks. Protoconch low, we only had weathered material available to study and therefore the sculpture could not be examined; R1 regularly, finely ribbed; R2 very densely ribbed, ribs curved towards aperture. Remarks. Protoconch, normally elevated (not higher or lower than what would be expected from the overall shell shape), it is matte, without any notable sculpture; R1 regularly ribbed; in fresh shells ribs sharp and strongly curved towards aperture; R2 very densely ribbed, ribs with T-shaped cross sectional view.

Dicharax tangmaiensis (Chen & Zhang, 2001)
Remarks. Protoconch low, lacks any signs of spiral striation; R1 with widely spaced ribs but no spiral lines; R2 short, with ribs which are curved towards the aperture.

Dicharax theobaldi diyungensis (Godwin-Austen, 1914)
Alycaeus theobaldi var. diyungensis Godwin-Austen, 1914: 401-402, pl. 138, fig Remarks. Same as in theobaldi solidus, but R2 is longer. Remarks. The entire shell is quite weathered, but the following observations could be made: protoconch low, without spiral striae; R1 glossy, with widely spaced, strong ribs (present only near the suture) and without spiral lines; R2 short, with dense, low ribs; R2 of fresh shells is probably smooth. Remarks. Protoconch low, seemingly smooth but rather matte; R1 somewhat regularly ribbed; rib density of R2 higher than that of R1, ribs on R2 low, not curved, rather sharp, connected to each other near tube (similar to Japanese "Awalycaeus" and "Cipangocharax" species); for more details see the original description. Remarks. The holotype is in a strongly corroded state; therefore, the sculpture could not be examined in detail. This species is putatively placed in Dicharax due to the overall smooth shell and the fringed aperture. Remarks. Only the holotype is known. The outermost shell layer is entirely weathered and the sculpture is not visible. The protoconch is seemingly low. Based on this character, A. barowliensis is tentatively classified in the genus Dicharax. Remarks. Protoconch somewhat elevated, rather glossy without notable sculpture; first whorl of R1 irregularly, finely ribbed, with ribs becoming stronger, rarer and more regular towards end of R1; R2 with 24-28 elevated, blunt, regular ribs; for description of cross-sectional view see original description. Type locality. "Kopamedza Peak Naga Hill, 8-9,000 feet, in forest".
Remarks. Protoconch low, glossy, no spiral lines visible; R1 very finely, regularly ribbed without spiral lines; R2 moderately long, with regular ribs, which are curved towards the aperture, however the space between the ribs is much larger than in typical Dicharax.
Material examined. Photographs of the holotype (MZB 19025) were examined. Remarks. Protoconch low without spiral striae; R1-R3 smooth but spirally striated on the umbilical side. This spiral striation is assumed not to be homologous with that of Metalycaeus species (i.e., it is probably part of the lower shell layers, not elevated from the shell surface), and similar to the structure observed in some D. depressus shells (see ). R2 smooth from above, with ca. seven narrow lines, no elevated ribs discernible.
Remarks. No specimens were examined. The general shape and the sculpture of the species is similar to Dicharax longituba according to the original description. Therefore, Alycaeus crassicollis is tentatively classified in Dicharax. Remarks. Protoconch moderately elevated, matte, no spiral lines visible; R1 rather regularly ribbed, also without spiral lines; R2 relatively short, with regular, widely spaced, sharp ribs.
The placement of the species in the genus Dicharax is based on the absence of spiral striation on the entire shell; however, the sharp R2 ribs are characteristic of the genus Chamalycaeus. The shape of protoconch shows some variation within species. Namely, typical crispatus and typical cristatus minimus shells have only slightly elevated protoconchs, whereas it is characteristically Chamalycaeus-like (strongly elevated) in D. crispatus makarsae specimens. Remarks. Protoconch rather low, R1 with strong, widely spaced ribs which are most prominent near the suture and disappear on the edge of the body whorl; R2 of normal length, ribs blunt, and at the anterior end of the region ribs curved towards aperture.

Dicharax (?) crispatus rywukensis (Godwin-Austen, 1914)
Alycaeus crispatus var. rywukensis Godwin-Austen, 1914: 373-374, pl. 154 Type locality. "Torúpútú Peak, 7000 feet". Material examined. Toruputu Peak, Dafla Hills, coll. Godwin-Austen, NHMUK 1903.7.1.2497 (lectotype: here designated, and 6 paralectotypes). The type sample contained two vials, one with two and the other with four shells. The one with four shells contained three larger shells and one which was conspicuously smaller. That smaller shell differs from the larger ones in terms of other shell characters, such as the spire height (lower than the others), the sculpture of R1 (smoother than the others), the strength of the swelling on R3 (less elevated than that of the others), and the lobes of the peristome (less conspicuous than those of the others). Therefore, one of the larger shells is selected here as lectotype to avoid further confusion.
Remarks. Protoconch low, rather matte, no spiral lines visible; R1 irregularly, finely, densely ribbed, some spiral lines visible but these are probably part of the layer below the outermost one; R2 relatively short, smooth, only lighter, narrow and slightly thicker, darker stripes alternating. Remarks. Protoconch low, glossy, no spiral lines visible; R1 without spiral striation; R2 very long, ribs very slender, relatively sharp, straight; at the edge of the body whorl space between ribs is ca. 3-4 × larger than the ribs themselves.
Remarks. Protoconch low, without spiral structure; R1 smooth, glossy, without spiral striation; R2 long, with straight, low ribs; in some specimens, especially near the beginning of the tube, the ribs look as if they have been "pushed" in an anterior direction (ribs similar to typical Dicharax, but lower).
The lectotype designation of Aravind and Páll-Gergely (2018) was invalid, because no explicit statement was made to designate the lectotype. Thus, we here designate that shell to be the lectotype, which was named as such, and figured by Aravind & Páll-Gergely (2018: fig. 1D).

Dicharax (?) gemma (Godwin-Austen, 1914)
Alycaeus gemma Godwin-Austen, 1914: 355-356, pl. 149 Remarks. All three available shells were weathered, but the following observations could be made: protoconch low, without spiral lines; R1 with rough wrinkles near the suture, but the region is without spiral lines; R2 very short, the fine structure of the ribs could not be observed. Remarks. Protoconch low, matte, without spiral striation; R1 with regular, strong, rather dense ribs, near the suture the ribs are sharp, elevated; R2 long, with rather dense, sharp ribs; at the anterior end of R2 the ribs are slightly bent in anterior direction.

Dicharax (?) khasiacus (Godwin-Austen, 1871)
Alycaeus Khasiacus Godwin-Austen, 1871: 90, pl. 3, fig. 4 Remarks. Protoconch low, glossy, without spiral lines; R1 also glossy, without any notable sculpture; R2 moderately long, with lamella-like ribs, which are straight in Remarks. The holotype was strongly weathered, but no spiral striation could be found on the relatively intact protoconch and R1 surface; the protoconch was also low, therefore this species is classified in Dicharax. The R2 region was so weathered that its original structure could not be seen.  Remarks. The holotype is strongly corroded. We include this species in Dicharax due to the relatively low protoconch.

Dicharax (?) levis (Godwin-Austen, 1914)
Alycaeus levis Godwin-Austen 1914: 394, pl. 138, figs 3, 3a. Remarks. The entire shell was strongly weathered; the fine sculpture could not be fully examined. Protoconch low, no spiral lines visible; R1 without any recognisable sculpture; R2 moderately long, ribs dense and their fine structure could not be examined. The species is placed in the genus Dicharax on the basis of its low protoconch. Type locality. "Logtak Lake, Munipur (...) on a low hill near the northern shore".
Remarks. Protoconch elevated, but no spiral lines were visible; R1 with widely spaced ribs without spiral striae; R2 relatively long with widely spaced, sharp ribs.

Dicharax (?) magnus (Godwin-Austen, 1893)
Alycaeus magnus Godwin-Austen, 1893: 594. Alycaeus (Alycaeus)  Remarks. Protoconch low, weathered, no spiral lines visible; R1 also without spiral lines; R2 very long (similar to Chamalycaeus heudei), some of the ribs have a horizontal projection in an anterior direction; near the suture these projections sometimes reach the neighbouring ribs; the entire shell is somewhat weathered, therefore it is not possible to decide if all ribs had these horizontal projections or only some of them. Remarks. Protoconch low, glossy, without spiral striation; R1 with dense, rather regular, low ribs and without spiral striation; R2 relatively long, with darker wider and lighter narrower stripes alternating, the overall surface of R2 is smooth.  Remarks. The original description does not mention the number of available specimens. Thus, the shell labelled as holotype is considered to be a syntype. Protoconch low, without spiral striation, R1 with low, rather regular ribbing; surface of R2 wavy, ribs are blunt and only slightly elevated from the surface. Remarks. Protoconch low, rather glossy, no spiral lines visible; R1 smooth, without spiral striation, only some irregular, rough wrinkles visible near the suture; R2 moderately long, nearly smooth with alternating darker and lighter stripes.
Remarks. Protoconch rather low without any signs of spiral striae; R1 regularly ribbed without spiral striation; R2 long with widely spaced, sharp ribs (typical for Metalycaeus). Remarks. Protoconch low, without spiral striation; beginning of R1 nearly smooth, its end with rather widely spaced, wide, but low ribs; R2 long, with rather sharp, straight ribs.  Remarks. Protoconch low, without spiral striation; R1 glossy, without any sculpture; R2 short, with low ribs, not bent in any direction.

Dicharax (?) obscurus (Godwin-Austen, 1914)
Alycaeus obscurus Godwin-Austen, 1914: 378-379, pl. 154 Remarks. Protoconch slightly elevated, but no spiral lines visible; R1 also without spiral lines; R2 moderately long with relatively dense but spaced, sharp ribs. The slightly elevated protoconch and the morphology of the ribs is similar to that of Chamalycaeus, but they are closer to each other than usually occurs in that genus. Remarks. Protoconch low, no spiral lines visible; R1 also without spiral striation; R2 short, with dense ribs; the fine morphology of the ribs could not be examined due to corrosion.

Remarks.
The type specimens could not be found in Beijing during a recent search, and they are thus considered lost. The original description is not sufficient for correct generic placement. A Dicharax species have been collected near the type locality of C. panshiensis (Guoyi Zhang pers. comm.) reminiscent of Korean and Japanese Dicharax species, which suggests that C. panshiensis belongs to the genus Dicharax. However, since no specimens are available and the original description is also useless, collection of topotypic specimens would be necessary.

Remarks.
Protoconch low, no spiral lines visible; R1 glossy, without notable sculpture; R2 short, with alternating thicker/darker and narrower/lighter stripes; the overall surface of R2 is seemingly smooth. Remarks. Protoconch low, without spiral striae; R1 also without spiral striae and with low, dense, regular ribs; R2 with low, regular ribs; the entire R2 surface is wavy.

Dicharax (?) sandowayensis (Godwin-Austen, 1914)
Alycaeus sandowayensis Godwin-Austen, 1914: 423-424, pl. 139 Remarks. The specimen in lot 1903.7.1.2666 is weathered, so the original sculpture could not be fully examined, but a second type lot of A. sculpturus contained four shells in relatively good condition (NHMUK 1903(NHMUK .7.1.2667. Protoconch moderately elevated, no spiral lines visible; R1 with widely spaced, strong ribs and without spiral lines; R2 of normal length, with widely spaced, sharp ribs. Remarks. The syntype was strongly corroded. Protoconch low without spiral lines; R1 smooth with rough wrinkles near the suture; R2 moderately long, the fine structure of the ribs could not be examined because the ribs have been damaged. Remarks. This species fits the range of morphological variation of Dicharax fimbriatus, which is an extant species from the same geographic area. However, we find it more useful to keep this taxon as a separate species due to its age. The strikingly similar appearance of an early Miocene species (Aquitanian, 23-21 Ma) to species living today indicates the high level of morphological stability of Dicharax.
Material examined. Naga Hills, NHMUK 1903.7.1.2622 (3 syntypes). Remarks. Protoconch low, without spiral structure; R1 rather regularly ribbed without spiral structure, R2 long, with sharp, straight, low ribs. The sharp ribs are characteristic for the genus Dicharax, but in case of A. stoliczkii the ribs are much lower than in any Chamalycaeus species. Therefore, based on the low protoconch without spiral lines, we classify this species in the genus Dicharax. Remarks. Protoconch low, without spiral striae; R1 with irregular, low ribs and without spiral striation; R2 short, with alternating wider/darker and narrower/lighter stripes; entire surface nearly smooth.  Remarks. Protoconch rather low, without spiral striae; R1 regularly ribbed without spiral striation; R2 long with widely spaced, sharp ribs. Alycaeus succineus is classified in Dicharax on the basis of the low protoconch and the absence of spiral striation, but the elevated, sharp R2 ribs are characteristic of the genera Metalycaeus and Chamalycaeus. Remarks. Protoconch low, no spiral lines visible; R1 with rather regular ribs and without spiral striation; R2 long, with widely spaced, ribs lamella-like, straight, but relatively low (typical Chamalycaeus character).
Protoconch low, rather matte, very finely granulated; R2 with 30-32 low, blunt, irregular ribs, which are usually in contact with each as they near the tube; at the edge of the body whorl they are distinct, the gap between them being slightly smaller than the width of a rib; no spiral lines visible on R1.
Type locality. "Koogejima, Sekizen-mura, Ochi-gun, Ehime-Ken". Material examined. NSMT-Mo 60073 (holotype). Remarks. Protoconch low, very finely granulated, only slightly glossy; R2 with ca. 23 relatively low riblets occasionally fused to each other near the tube; space between the riblets at the edge of the body whorl is roughly as wide as the ribs; no spiral lines visible on R1.
Remarks. No specimens were examined by us, but the original description provides enough information of the key characters: protoconch low, glossy; R1 with rather dense, strong ribs; R2 short, with very dense, low ribs; R3 longer than R2, without swelling.
Remarks. Protoconch low, finely granulated, rather matte; R2 with ca. 26 low, blunt, irregular ribs, which are connected to each other near the tube, gradually becoming free towards the edge of the body whorl (here the distance between neighbouring ribs is very small, much less than the width of a rib); no spiral lines visible on R1.

Dicharax (?) cyclophoroides (Pilsbry & Y. Hirase, 1909)
Alycaeus cyclophoroides Pilsbry & Y. Hirase, 1909b: 9, pl. 5 Remarks. Protoconch low, finely granulated, rather matte; R2 with ca. 28 low, blunt riblets, which form connections with each other near the tube; they are distinct at the edge of the body whorl, the space between them is slightly smaller than the width of a rib; no spiral lines visible on R1.
Protoconch low or slightly elevated; R2 with ca. 26, relatively elevated and distinct ribs which are not in contact even at near the tube; at the edge of the body whorl the distance between the ribs is more than twice as wide as the width of a rib; there are no spiral lines visible on R1.
Remarks. Protoconch low, very finely granulated, moderately glossy, no spiral lines visible; R2 with ca. 14-20 (14 Sakurai coll., 20 on the holotype) low, blunt ribs; ribbing resembles irregular wrinkled surface; near the tube some ribs reach the neighbouring ones, and partly fuse with them; at the edge of the body whorl the ribs are not in contact, the spaces between ribs almost reaches the width of a single rib; no spiral lines on R1.
Remarks. Protoconch low, glossy; R2 with 18-22 low, blunt ribs connected to each other near the tube, but free at the edge of the body whorl (here the distance between two ribs is ca. as wide as the width of a single rib); no spiral lines visible on the teleoconch.
Remarks. The shell we examined was weathered, only the shape of protoconch (low) could be seen and its sculpture was not visible; R2 with ca. 22 low, blunt, irregular ribs which are joined to their neighbours at least near the tube; no spiral lines visible on the shell.

Remarks.
Protoconch similar to that of biexcisus; R2 with 16, widely spaced, low, blunt ribs; spaces as wide as or slightly wider (at the edge of the body whorl) than individual ribs; in the case of the three shells in the Sakurai collection some of the ribs on R2 are joined to the neighbouring ones near the tube; no spiral lines visible on R1. Operculum relatively slim with low outer belt and without nipple (see also original description).
Dicharax (?) kurodatokubeii (Minato, 1987) Chamalycaeus kurodatokubeii Minato, 1987a: 222-223, 224-225 Remarks. The protoconch of the holotype probably has a growth disorder, and its sculpture could not be fully examined. It was low, very finely granulated, and the last 0.25 of the whorl was wrinkled. The specimens in the Sakurai collection have normally developed protoconchs, which were low and finely granulated, without spiral lines; R2 has ca. 30-32 low, blunt ribs; most ribs are completely merged with the neighbouring ribs nearer the tube; ribs free at edge of body whorl; space between ribs ca. 2 × as wide as an individual rib; no spiral lines visible on R1.

Dicharax (?) miyazakii (Takahashi & Habe, 1976)
Chamalycaeus miyazakii Takahashi & Habe, 1976: 27-28, text fig. 1. Chamalycaeus miyazakii -Minato 1988. Remarks. Protoconch low, very finely granulated, but rather glossy; R2 with ca. 20 low, blunt riblets; they are very low near the tube (it is difficult to decide whether they overlap or not); at the edge of the body whorl the space between the ribs is roughly as wide as a single rib; no spiral lines visible on R1; operculum relatively thick, at least as thick as that of C. kiuchii.
Material examined. NSMT-Mo 64355 (holotype). Remarks. Protoconch low, very finely granulated, moderately glossy (the protoconch of the holotype was partly weathered); R2 with ca. 20 low ribs, clearly separated at edge of body whorl; generally ribs more distinct than in S. itonis itonis; here space between ribs is as wide as individual ribs; no visible space between the ribs closer to the tube, except for those situated close to the end of the tube; no spiral lines visible on R1.

Dicharax (?) nakashimai ditaceus (Minato & Yano, 2000)
Chamalycaeus (Sigmacharax) nakashimai ditaceus Minato & Yano, 2000: 129-133 Remarks. Protoconch low, moderately glossy, very finely granulated, with fine wrinkles on the last 0.25 of whorl; R2 with ca. 28 low, hardly separable, blunt ribs; close to the tube boundary between ribs hardly visible, they possibly overlap; at the edge of the body whorl there is some distance between ribs, smaller than width of an individual rib; no spiral lines visible on R1.

Dicharax (?) placenovitas
Operculum with a big central nipple on its inner side; however, the outer belt was absent. The columellar margin of the aperture is not sinuated. The aperture forms a connection between the Cipangocharax-type and normal-type aperture.

Remarks.
No specimens were examined by us, but the photographs of the original description provide sufficient details of the fine sculpture. Protoconch low, rather glossy; R1 with widely spaced, elevated, sharp ribs; R2 with much denser, blunter ribs.
Dicharax spiracellum (A. Adams & Reeve, 1850) was described from Borneo, based on shells from the expedition of HMS Samarang (1843-1846). Alycaeus kurodai Pilsbry & Y. Hirase, 1908, described from the Korean Cheju Island, is conchologically identical to Dicharax spiracellum and is a junior synonym of the former species (Páll-Gergely 2019). The type specimens of Dicharax spiracellum were probably obtained when the Samarang visited Cheju Island, and the specimens were most likely mislabelled (Páll-Gergely 2019). Therefore, the type locality of D. spiracellum was emended to "probably Cheju Island, South Korea" (Páll-Gergely 2019). (Kuroda & Miyanaga, 1943) the ribs, but some of them join with their neighbours; distance between ribs at edge of body whorl 1-2 × as large as a rib width; no spiral lines visible on R1.
Remarks. Protoconch low and finely granulated, the last 0.25 of the protoconch whorl is finely wrinkled; R2 with ca. 34-40 low, blunt ribs; they are situated close to each other near tube, but probably do not form connections with each other; distance between ribs at the edge of body whorl ca. as wide as a rib width; R1 with extremely fine spiral lines between ribs (probably not homologous with the spiral striations in Metalycaeus species).
Remarks. Mentioned traits are the same as those of the nominotypical subspecies.
Remarks. Protoconch low, very finely granulated, moderately glossy, but the protoconch of the holotype was slightly weathered; however, those in the Sakurai collection were not; R2 with ca. 25 low, blunt, but well separated ribs; even near the tube the ribs seem to be free from each other; distance between ribs at edge of body whorl ca. as wide as a rib, or slightly wider; no spiral lines visible on R1. Type locality. "extended region of limestone area of Saruda-do Cave, Okina, Hidakamura, Takaoka-gun, Kochi Prefecture".

Remarks.
No specimens were examined by us, but the photographs of the original description provide sufficient details of the fine sculpture. Protoconch low, rather glossy; R1 with relatively dense, strong ribs; R2 with low, very dense ribbing.
Diagnosis. Shell small to very large (3.5-9 mm), globose, sometimes the body whorl is angled or keeled; protoconch smooth, not spirally striated; R1 usually very finely reticulated due to fine radial ribs and fine spiral striation, or smooth; R2 short to long, usually without ribs (superficially smooth, with alternating lighter and darker stripes); R3 practically absent (the inner opening of the sutural tube is situated close to the aperture). Operculum thin, usually proteinaceous ("horny"), in some species can be thicker, calcified. Central tooth with 5-7 cusps, broad, central cusp blunt.
Differential diagnosis. The combination of the globular shell, the reduced sculpture (only very fine spiral and radial lines are present), and the absence of the R2 region characteristic for the vast majority of alycaeid species make Dioryx species distinguishable from other alycaeid genera.
Distribution. Dioryx is distributed from the southeastern Himalayan region to Taiwan in the east, and down to the northern part of the Malay Peninsula and southern Vietnam in the south (Fig. 7).
According to the original description of A. cochinensis, only a single shell was found "stuck on the same slab with Alycaeus gibbus" and originated from the collection of Hugh Cuming. We were unable to locate the holotype in the type collection of the NHM, but found a shell in the general collection labelled "Dioryx cochinensis G.-A. ms., Cochin China (Cuming)", with a black glue mark on its body whorl indicating that it was previously mounted as indicated in the original description. This specimen is identical with the figures of Godwin-Austen (1914) (characteristic shell shape from apertural view: pl. 156, fig. 7; and the very short tube: pl. 156, fig. 7a). Therefore, we identify this specimen as the holotype of Dioryx cochinensis. The measurements provided by Godwin-Austen (1914) are the following: "major diam: 5.5; alt. axis 4.75 mm". Our measurements of the specimen are, however, somewhat larger, namely D: 6.1 mm, H: 7 mm. This is probably due to the inaccuracy of the original measurements (as usual in Godwin-Austen's specimens), and we do not question the status of the specimen.

Dioryx compactus (Bavay & Dautzenberg, 1900)
Alycaeus ( Remarks. Five shells in the Senckenberg Museum (Tonkin, Bac-Kan, Cho-Ra, leg. Messager, coll. Rolle ex coll. Bosch, SMF 192287) were labelled as syntypes, although they clearly belong to a different species than the single syntype in MNHN Paris, which agrees with the figures in Bavay and Dautzenberg (1900b). This single shell is identical to Dioryx distortus, but smaller. A comprehensive revision would probably reveal that the two names are synonyms.
The following remarks are based on the syntype from Paris: protoconch matte; R1 with irregular, very weak, widely spaced ribs and dense spiral striae of the same strength, although due to small space between spiral striae, they are much more conspicuous than the rare radial lines; R2 long, with very thin lighter and darker thicker stripes, the overall surface is smooth, glossy.

Dioryx distortus (Haines, 1855)
Cyclostoma distortum Haines, 1855: 158, pl Remarks. Protoconch matte, without spiral striation; the overall sculpture very weak; first whorl of R1 with spiral striation and widely spaced, irregular radial lines; later spiral lines disappear and radial lines become regular and dense; R2 very long, reaches ca. 150°, it is entirely smooth, only slimmer light and thicker darker stripes alternate.
Remarks. The original description does not mention the number of examined specimens. Thus, we consider the specimen labelled as holotype (SMF 39298) syntype.

Dioryx pilula (Gould, 1859)
Alycaeus pilula Gould, 1859: 424-425. Remarks. Protoconch extremely finely granulated, rather matte; R1 with irregular growth ridges and very fine spiral striation; R2 relatively short, with extremely fine alternating wider/darker and slimmer/lighter stripes. Johnson (1964) did not find the type lot in the Smithsonian Museum. The sample we examined was collected at the type locality.

Dioryx ruyangensis Hu, Yin, & Chen, 2004
Remarks. The holotype (IZCAS TM 132794) and a paratype (IZCAS TM 132795-132805) were photographed by one of us (Meng Kaibaryer). The shell height was 4.7 and 4.6 mm respectively, whereas it is given as 7.1 mm in the original description. Moreover, the examined specimens were much more corpulent than the one imaged in Hu et al. (2004), indicating that they belong to another species. Consequently, the types of this species are considered lost.
According to Johnson (1973) syntypes are also present in the USNM (inventory number: 472337).

Remarks.
Protoconch smooth, R1 with irregular, very fine radial lines; R2 moderately long (ca. 90°), seemingly smooth, with alternating lighter/slimmer and darker/ thicker stripes. Etymology. The replacement name rotundus (Latin for spherical, globular, round, circular) refers to the shell shape of this subspecies.
Alycaeus (Dioryx) urnula var. globosus Godwin-Austen, 1914 is a junior primary homonym of Alycaeus globosus H. Adams 1870. Here we propose rotundus as a replacement name for the junior homonym.
Diagnosis. Shell small to very large (D: 3-10 mm), spire usually low, protoconch usually elevated, spirally striated (key character); spiral striation of protoconch very rarely absent (see under M. laevis); R1 usually reticulated with sometimes prominent radial ribs; spiral lines always present on the teleoconch; R2 rarely short, usually long to very long, sometimes entirely smooth, but typically with widely spaced, straight, sharp ribs; R3 usually well-developed, although can be reduced. Operculum thin or relatively thickened, sometimes with funnel-shaped outer surface caused by the modification of the multispiral outer laminae. Radula usual for the family (central tooth with five cusps, broad, central cusp pointed).
Differential diagnosis. Metalycaeus is recognised based on the spirally striated protoconch, which distinguishes Metalycaeus from species assigned to all other alycaeid genera.
Distribution. Metalycaeus is widely distributed from the southeastern Himalaya to the south of Honshu Island (Japan) and the northern islands of the Philippines, but it does not extend any further south than northern Laos and Vietnam (Fig. 9).
Remarks. The type species of Raptomphalus (Metalycaeus magnificus) (Fig 31B) and M. oakesi have a prominently keeled umbilicus which serve as the distinctive character for the genus Raptomphalus. A less prominently keeled umbilicus is observable in other species, such as Chamalycaeus vulcani and Metalycaeus brahma, which can be interpreted as intermediate forms between the non-keeled umbilicus of alycaeids and the keeled umbilicus of Raptomphalus. Moreover, a variety of Metalycaeus brahma has much less prominent umbilical keel than typical species in the genus. Therefore, the keeled umbilicus cannot serve as a distinctive character between genera. Consequently, Raptomphalus is a synonym of Metalycaeus.
For sake of simplicity, this genus is divided here into typical and atypical (or questionable) species. The first includes those having sharp, widely spaced R2 ribs, whereas the second includes species with R2 sculpture other than typical, including those which could not be examined.
Type locality. "Bhutan Frontier, probably on Eastern, or Aka Hills, side".
The variety "M. brahma var." has a much less prominent keel inside the umbilicus, which supports our view regarding the invalid status of Raptomphalus.
Remarks. Protoconch elevated, spirally striated; R1 with irregular ribs and spiral striae of ca. the same strength, or slightly even stronger than the ribs; R2 relatively short, with alternating darker/wider and slimmer/lighter stripes; its surface is nearly smooth.
Alycaeus neglectus Heude, 1885 belongs to the genus Metalycaeus due to the spirally striated protoconch. This is the case even if it is treated here as a junior synonym of Metalycaeus rathouisianus (Heude, 1882). Thus, A. neglectus Godwin-Austen, 1914 is a primary as well as a secondary junior homonym of Alycaeus neglectus Heude, 1885 and thus, a replacement name (godwinausteni) must be given.

Metalycaeus kengtungensis (Godwin-Austen, 1914)
Alycaeus kengtungensis Godwin-Austen, 1914: 409, pl. 139 Remarks. The whole shell is weathered; therefore, the sculpture could only be examined in very small regions of the shell. Protoconch elevated, some slight signs of spiral striation are visible; R1 regularly ribbed, spiral lines are not visible; R2 very long, the ribs are very widely spaced and sharp.
Remarks. Protoconch elevated, spirally striated; R1 with very strong ribs with very weak spiral lines between them; R2 short, with widely spaced, sharp ribs, which are usually slightly bent in the direction of their anterior neighbours.
Remarks. Protoconch elevated, spirally striated; R1 with rather regular, widely spaced ribs with somewhat weaker spiral striae between the ribs; R2 long, with sharp, widely spaced ribs.
Remarks. Protoconch conspicuously elevated from dorsal surface, its end with inconspicuous spiral striations; R1 with irregular, widely spaced ribs and fine spiral sculpture; R2 with dense, sharp, elevated ribs.
No type specimens of Alycaeus expansus were reported in American museums (Johnson 1973). We were not able to examine the types deposited in the Beijing Museum before the revision of Chinese Alycaeidae ), but could do so now. The general shell shape, colour, sculpture, and the lengths and proportions of R2 and R3 agree with those of A. muciferus, which was described from the same type locality. Consequently, we move Alycaeus expansus to the synonymy of A. muciferus.

Metalycaeus nipponensis
In the examined sample, 91 specimens had an operculum, and of those 53 of them had the outer black circle present. In case of 27 specimens the outer circle was entirely missing, and in 11 cases only small fragments of the rings remained.
All four shells were strongly weathered, but the characteristic elevated protoconch was recognisable. Moreover, some indication of spiral striation was visible on both the protoconch and R1, therefore the classification of M. oakesi in Metalycaeus is justified. R2 long, with widely spaced, sharp ribs. Remarks. Protoconch elevated, finely spirally striated; R1 with sharp ribs and Type locality. "ad Teria Ghát".
The constriction is longer than in usual Dioryx, and the protoconch is spirally stri-

Remarks.
The specimens labelled as the types (Tashan Town, Zayu County, Nyingchi City, Tibet Autonomous Region, China, leg. Chen De-Niu, 1980.7.13, IZCAS TM_094538, holotype; IZCAS TM_094540, paratype) of C. zayuensis represent a species different from the one characterised in the original description. Namely, the real C. zayuensis has a smooth R2 with dense stripes, and finely ribbed R1, whereas the ones we examined have elevated, sharp, widely spaced R1 and R2 ribs. Furthermore, the ones in the Beijing Museum have sharp swelling on R3 with an incision at the middle, whereas the ones in the original description possess a relatively low, simple R3 swelling.
Chamalycaeus zayuensis was previously moved to the genus Metalycaeus based on the spiral striation (Zhouxing and Wechuan 2015;.
Remarks. Protoconch relatively elevated, some spiral striation is visible on the photographs; R1 with relatively widely-spaced ribs and fine spiral striation; R2 + R3 ca 90° combined R2 slightly shorter than R3; R2 ribs sharp but relatively low, similar to those on R1; R3 with a low but relatively sharp swelling. Remarks. The entire shell weathered, but the following observations could be made. Protoconch rather elevated, some spiral striae are recognisable near the suture; R1 without visible spiral lines; R2 short, very densely ribbed, but the fine morphology of the ribs could not be seen. Remarks. Protoconch moderately elevated, spiral lines visible on the last whorl of protoconch (although there was no clear distinction between protoconch and teleoconch); R1 irregularly ribbed, ribs low but relatively sharp at the end of R1; there are signs of very weak spiral lines between ribs on R1; R2 ribs not erected but situated horizontally. For more details see the original description.
Diagnosis. Shell very small to medium sized (D: 2.5-6 mm), globose triangular, usually higher than wide; protoconch smooth, without spiral striation; R1 usually with strong, widely-spaced ribs and weak spiral striation; R2 smooth to prominently ribbed (in those cases not different from R1), very short, pyriform (in typical Cycloryx species) or somewhat longer in Pincerna-like shells; umbilicus often closed by the reflected columellar extension in many species. Operculum thin, in some species with a low circular structure, or calcareous ridges radiating outwards of the nucleus on the outer surface. Radula of a single species is known, see Table 1 (central tooth with 5 cusps, broad, central cusp pointed).
Differential diagnosis. See Remarks.
Distribution. The distribution of Pincerna seemingly consists of two disjunct geographic areas, namely the southeastern Himalaya to northern Vietnam and northern Laos, and Sumatra, the southern part of the Malay Peninsula, and northern Borneo (Fig. 40).
Remarks. The relationship between Alycaeus, Pincerna, and Cycloryx is the most problematical point of the current revision. The genus Cycloryx Godwin-Austen, 1914 (type species: Cyclostoma constrictum Benson, 1851, OD) was erected as a subgenus of Alycaeus Gray, 1850, and was described on the basis of the ovately conoid shell shape, the regular ribbing on the upper whorls, and the extremely short, often clubbed or pear-shaped sutural tube (Godwin-Austen 1914). Godwin-Austen (1914) only included species from northeastern India and Burma (Rakhin = Arakan, and the Shan States) in this genus. However, the diagnosis of Cycloryx matches several species extralimital to the distributional range as defined by Godwin-Austen, namely those from northern Vietnam, Borneo, China's Guizhou Province, the Malay Peninsula, and Sumatra. The most striking example is the Sumatran Pincerna yanseni and the northern Vietnamese Alycaeus costulosus, which both look so similar to Indian and Burmese species that it was challenging to find any differences between those two and the Indian and Burmese taxa. One of those "extralimital Cycloryx" is Alycaeus liratulus Preston, 1907, known from the Malay Peninsula and Sumatra, which has been placed in its own subgenus, Pincerna Preston, 1907. Originally, Pincerna was diagnosed on the basis of a "circular cup" on the outer surface of the operculum. The outer surface of operculum, however, has limited taxonomic value at the generic level in the Alycaeidae, especially since the outer rings have evolved in multiple alycaeid genera (Dicharax, Metalycaeus, Stomacosmethis; see this study and Páll-Gergely et al. 2017). Moreover, the most similar species to P. liratula, P. thieroti, lacks the circular cup on the outer surface of the operculum. Consequently, no important conchological characters distinguish Cycloryx and Pincerna, and thus, they have been synonymised (Páll-Gergely 2017). See also under Genus-level diversity (p. 13).
Pincerna is globular and sparsely ribbed, Stomacosmethis is triangular and densely ribbed. Stomacosmethis balingensis is globular, but densely ribbed, forming a connection between the two genera, but the radula morphology unambiguously indicates its position within Stomacosmethis. We retain the two genera separate due to the unique radular morphology of all known Stomacosmethis species. Furthermore, there are many species with typical features of both respective genera. See also under Alycaeus (p. 17).

Remarks.
Protoconch matte, no spiral lines visible; R1 strongly, regularly ribbed with hardly visible, extremely fine spiral striation; R2 extremely short, with ca. seven narrow, light stripes, the overall surface is smooth.
Some Indian species originally included in Cycloryx (e.g., P. graphica var. dihingensis, P. thompsoni, P. burrailensis) are so similar to P. costulosa that it was challenging to find any notable differences. Pincerna costulosa must evidently be classified in Pincerna in the face of the large geographic gap between it and the Indian/Burmese species.  Remarks. The spire is high, but the protoconch is relatively low, it is rather matte, without spiral lines; R1 with some spiral lines, especially at the end of the region; There are widely spaced, strong ribs on R1 which are bunt at the beginning, but sharp at the end of the region; R2 short, with elevated, sharp, widely spaced ribs with some weak spiral striation between the ribs. This species fits in the genus Chamalycaeus as well as into Pincerna. It is tentatively placed here due to the elevated spire. Further studies should focus on its systematic relationships. Remarks. Protoconch matte, R1 with strong, regular, widely spaced, sharp ribs without spiral striations; R2 short with ribs that are similar to the ones on R1 in morphology and density.
Smith (1895) advised considering all forms of Alycaeus globosus under one species because there is "such a general resemblance throughout the series". Although this is true, the size difference between pygmaea and muluana are extreme. If they were truly collected from the same site, then they should be treated as distinct species. However, the accuracy of the localities is unknown. This species was described as A. mangutensis by Godwin-Austen in 1914, and that name was later used as a valid taxon name (Gude 1921;Ramakrishna et al. 2010). However, the name Alycaeus (Dioryx) granum var. major Godwin-Austen, 1893 for the same taxon was validly introduced, and is available. Thus, the species must be called Pincerna major (Godwin-Austen, 1893), and the name Alycaeus mangutensis Godwin-Austen, 1914 is a junior objective synonym. Remarks. Apex matte, no spiral lines visible; R1 with rather regular, low ribs and extremely fine spiral striation (mostly visible near the suture); R2 moderately long, smooth, narrow lighter and thicker darker stripes alternating.
The tube length is variable within this species (based on Chinese and Vietnamese samples, B. Páll-Gergely, unpublished information); in some specimens its length can reach to a 0.5 whorl, whereas in others it is shorter than a 0.25 whorl.  Remarks. Entire shell somewhat weathered; protoconch matte; R1 regularly, densely ribbed, spiral striation not visible, but additional, lower radial lines present between the ribs; R2 very short, ca. five ribs, similar to those on R1 in density.
This species may be conspecific with P. graphicus var. dihingensis because there is only a slight difference in the density of ribbing (coarser and more oblique in thompsoni). Pincerna thompsoni has a completely closed umbilicus, but due to the lack of large shell material we are unable to determine whether this represents individual variability or a stable character. Alternatively, the closed umbilicus may be a feature of more mature (more developed) specimens. Remarks. Protoconch glossy, first 1.75 whorls of R1 with low, relatively dense, regular ribs and weak, dense spiral striation; this sculpture gradually changes to a more sparsely ribbed region, which spans ca. 0.5 a whorl; R2 and tube very short, with eight or nine ribs very narrow, only slightly elevated from the surface; for description of the fine structure of the microtunnels, see original description.
Diagnosis. Shell small to very large (D: 3-13 mm), usually brightly coloured yellow or orange; shell shape triangular or depressed triangular; protoconch smooth without spiral striation; R1 usually finely reticulated, without prominent ribs; R2 very short, usually roughly, weakly wrinkled, R3 long, with blunt swelling. Operculum thin, outer surface smooth or with outer, elevated, trumpet-like projection. The outer operculum surface can also be finely granulated, flaky or have short calcareous spikes (Foon and Liew 2017). Central radular tooth elongated, usually with a single central cusp only, or central cusps with one or two small cusp at each side.
Differential diagnosis. Most species classified in this genus were previously described in Alycaeus. However, Alycaeus species are characterised by a very long R2, whereas the R2 is extremely short is Stomacosmethis. Pincerna species possess a globular shell with more widely spaced ribs, and they are usually not colourful. The distinction of Stomacosmethis and Pincerna requires further examination. See also under Pincerna (p. 147).
Distribution. This genus is distributed in the tropical forests of the Malay Archipelago (Malay Peninsula, Borneo, Java, Sumatra, Sulawesi).

Remarks.
This genus was originally diagnosed based on the calcareous, pipe, tongue or cup-shaped structure on the outer side of the operculum. Since the circular opercular structures have evolved multiple times, this genus must be re-diagnosed. The type species belongs to a clearly delineable group of the Alycaeidae having triangular, colourful shells, dense, fine ribs and short tube, which is now called Stomacosmethis. See also under S. balingensis, which is exceptional in terms of shell shape.

Stomacosmethis fultoni degenerans
Remarks. Protoconch without spiral lines, rather matte; R1 with rather regular, strong, sharp ribs and very weak spiral lines; R2 very short, with alternating darker/wider and lighter/narrower stripes; lighter stripes are very slightly elevated from the surface.
of Pfeiffer (1861). Hendriks et al. (2019) studied the phylogeography of S. jagori from Borneo. Given that the species is described from Java, the identity of the Bornean samples needs to be revised.
Protoconch glossy, without spiral lines; R1 with irregular, low ribs, very weak spiral striation in-between; R2 very short, with alternating darker/thicker and lighter/narrower stripes somewhat elevated from the surface; overall surface of R2 irregularly wrinkled.
Remarks. According to the original description this taxon differs from A. charasensis, A. costacrassa, A. selangoriensis, and A. kapayanensis in the formation of the body whorl and in slight differences in the shell sculpture. However, the differences in shell shape are not obviously visible on the photographs in Foon and Liew (2017). Instead, only very slight differences (if any) are to be seen, which we feel do not represent distinctive character traits on a species level. Therefore, we treat this taxon as a subspecies of S. kapayanensis.
Remarks. This taxon differs in minor traits (extent of the body whorl and strength of the sculpture) from S. kapayanensis and some other "species" described by Foon and Liew, therefore it is treated as a subspecies of S. kapayanensis.
Remarks. This taxon differs from Alycaeus kapayanensis selangoriensis and Stomacosmethis kapayanensis kapayanensis in characters of the operculum and shell sculpture, formation of the peristome and the body whorl. We believe however, that such characters are of minor taxonomic importance, and therefore, Alycaeus costacrassa is here considered a subspecies of S. kapayanensis.
Remarks. Alycaeus ikanensis is similar to the other taxa described by Foon and Liew, which are treated here as subspecies of Stomacosmethis kapayanensis. The original description states that A. ikanensis is most similar to A. costacrassa and differs from that species in its smaller and more slender shell. Again, these traits are enough for subspecific distinction, and slight differences in size and shell shape are insufficient for differences at the species level.

Remarks.
Protoconch extremely finely granulated, matte; R1 rather irregularly, finely ribbed with weaker spiral striation; R2 short, with alternating darker/thicker and lighter/slimmer stripes, which are somewhat elevated from the surface, the whole area is rather irregularly sculptured.
Foon and Liew (2017) described six new species from Peninsular Malaysia, which are similar to S. kapayanensis in all the important characters, and show only minor differences, such as fine sculpture (e.g., strength of radial vs. spiral striation), operculum thickness, and shell size and shape. Here we maintain those species (alticola, charasensis, costacrassa, ikanensis, kurauensis, selangoriensis and virgogravida) as subspecies of S. kapayanensis.
Remarks. According to the original description, Alycaeus kurauensis differs from Stomacosmethis kapayanensis in "having a wider ultimate whorl, thicker operculum with smooth exterior and more widely spaced radial ribs." These traits, in our opinion, are sufficient for distinction on subspecific level, but do not justify the distinctness at the species level. Therefore, this taxon is handled as a subspecies of S. kapayanensis.
Remarks. This taxon differs from S. kapayanensis in the larger shell, more expanded body whorl, thicker operculum, and the formation of the upper palatal section of the peristome. These differences seem to justify differentiation at the subspecific level only.
Remarks. This taxon differs from S. kapayanensis and its subspecies in only minor traits (shell and operculum sculpture, formation of whorls). Although described as a species in its own right, we suggest using it as a subspecies of S. kapayanensis.
Remarks. Alycaeus clementsi is very similar to Stomacosmethis kelantanensis in general shells shape and sculpture. The differences mentioned in the original description (shell size, peristome thickness, outer surface of the operculum, animal colour) are sufficient to distinguish them at the subspecific level only.

Remarks. Alycaeus expansus Foon & Liew is most similar to A. clementsi and
Stomacosmethis kelantanensis. Foon and Liew (2017) do not explain the differences between A. expansus and the other two taxa, but mention that the characteristic features of this species are the obtuse ultimate whorl, the strongly expanded peristome, the thick operculum and the animal colouration. Based on the photographs in the original description it is difficult to understand what the authors meant by "obtuse ultimate whorl", because the general shell and body whorl shape do not differ conspicuously from the other two taxa; it was supposed to mean the more rounded-looking ultimate whorl, especially for shells from the type locality (Junn Kitt Foon, pers. comm. 2020 June). Contrary to the original description, the peristome of S. kelantanensis is even more expanded than that of A. expansus. The animal colouration and the operculum thickness are characters which should not be used as distinguishing characters at the species level, especially because thickness of shell or operculum is highly dependent on the environment. Therefore, this taxon is treated as a subspecies of S. kelantanensis.
Alycaeus expansus Foon & Liew, 2017 is a primary homonym of Alycaeus expansus Heude, 1890. To our knowledge, the older name has not been used in this combination since 1899, thus no replacement name for Alycaeus expansus Foon & Liew, 2017 is necessary.
Remarks. Protoconch spirally striated at its very beginning and this sculpture turns to a rather finely granulated surface until the end of the protoconch (in case of Metalycaeus species the first 0.5-1.0 whorl is usually without spiral lines); R1 rather irregularly ribbed with somewhat weaker spiral striation; R2 very short, with ca. seven low ribs. The SMF 158410 sample contains three shells with prominent spiral structure and another three shells with only very slight indication of spiral lines.

Remarks.
Protoconch matte; R1 with irregular, low wrinkles and extremely fine spiral striation on the first 1-1.5 whorls; R2 very short, with alternating lighter/slimmer, and darker/thicker stripes, the lighter stripes slightly elevated from the surface; operculum with a very strongly elevated, expanded, trumpet-like structure.
Lothar Forcart selected a specimen (NMB 02266a) and labelled it as lectotype, but never published this action (Ambros Hänggi, pers. comm. 2020 June). Thus, here we designate the specimen selected by him as the lectotype.
Remarks. We had no opportunity to examine shells of Alycaeus matchacheepiorum. However, the original description is sufficient for correct generic placement. The protoconch is smooth, R2 very short and the entire teleoconch is finely ribbed.

Stomacosmethis perakensis (Crosse, 1879)
Alycaeus perakensis Crosse, 1879: 206-208, pl. 12, fig   Remarks. Protoconch glossy, without spiral lines; R1 with irregular, rather low ribs and very weak spiral striation in-between, but at the end of the region the ribs are more elevated, sharp; R2 very short, with alternating darker/thicker and lighter/narrower stripes which are somewhat elevated from the surface.
Stomacosmethis roebeleni may be a subspecies of A. perakensis although we refrain from treating it as such without further evaluation.
Remarks. Protoconch matte, no notable sculpture visible; R1 with rather regular, low ribs and very fine spiral striation; R2 short, with ca. 11 white, low, regular ribs. No operculum was found. Remarks. Protoconch very finely granulated, matte; R1 with rather irregular ribs and somewhat weaker spiral striation; R2 very short, with alternating thicker/darker and narrower/lighter stripes, which are slightly elevated from the surface.
Remarks. Protoconch elevated, no spiral lines visible; R1 with rather irregular, fine ribs, and somewhat weaker, dense spiral striae; R2 short, with roughly ten thicker/darker stripes, and much narrower/lighter stripes in-between, which are elevated from the surface. Type locality. "Sadong, Sarawak".
Remarks. Protoconch matte, without notable sculpture; R1 with fine, regular, low ribs and weaker spiral striation; R2 extremely short, with slightly elevated, white ribs. No operculum was found.
Remarks. Seems to be a distinct species based on original description: short R2 and triangular orange-coloured shell confirm its position within this genus.
Remarks. We had no opportunity to examine the holotype, but the original description and the photographs published therein provide sufficient information regarding the generic status of this species. The protoconch of the weathered holotype is smooth and R2 is short and regularly ribbed. Maassen (2006) questioned the generic status of A. wilhelminae based on its closed umbilicus; further investigation should focus on the value of this character. However, at the moment we see no need to classify it in a genus other than Stomacosmethis.
Nomina nuda "Alycaeus scepticus Theobald, 1863" Remarks. The name Alycaeus scepticus appeared in Theobald (1863: 377), but it was not made available. Blanford (1965: 101) mentioned that it turned out to be a variety of A. ingrami. Thus, Gude (1921) treated this name as a synonym of that species.
Manuscript names "Alycaeus pomatiaeformis Ancey" Remarks. A sample in the RBINS (Borneo, coll. Ancey, 28.VI.08) was labelled in this manner. The shell had a very wide peristome, and may be a new species.

Chamalycaeus satsumanus kiiensis Kuroda
Remarks. Museum samples from the Sakurai and Inuba collections in the NSMT bear this name, but was never been formally published (Hanshin Shell Club 1986).

Concluding remarks
After examining specimens of virtually all alycaeid taxa and the relevant literature, here we propose a novel classification of 320 accepted species and 43 subspecies into seven genera. The following conclusions can be made: (1) While the genera Dicharax, Dioryx, and Metalycaeus have unique character states which serve as diagnostic traits, the other four genera are defined based on a combination of shell characters. Distinctness between Pincerna and Alycaeus and between Pincerna and Stomacosmethis remain to be verified.
(2) The most important achievements of this study are the separation of Stomacosmethis from Alycaeus, and the identification of Dicharax and Metalycaeus species. We also found a common anatomical trait of the Alycaeidae (bursa copulatrix originates from the lateral side of the ovarium) besides the unique sutural tube-microtunnel system, which is probably a device for gas exchange.
(3) The species-level diversity (i.e., number of described species) is largely dependent on whether the splitting or lumping approaches were employed by the taxonomists who classified specimens from particular areas, which resulted in peculiar geographic differences in species diversity. (4) Various lines of evidence suggest the presence of three subgroups within the Alycaeidae (Alycaeus-Dioryx, Chamalycaeus-Dicharax-Metalycaeus, Pincerna-Stomacosmethis), which can be tested by future studies.

Relationships between genera
Morphological traits (shell, genital system, radula) presented here and unpublished molecular phylogenetic pattern suggest the presence of three groups within Alycaeidae. Firstly, the genera Alycaeus and Dioryx form a distinct group based on the blunt central cusp of radula and the position of the bursa copulatrix that starts posterior to the middle section of the ovarium. Their similarly rather large shell sizes (at least for many Dioryx species and all Alycaeus species) and overlapping distribution suggest these two genera might be closely related. Secondly, the genera Chamalycaeus, Dicharax, and Metalycaeus generally possess the depressed shell and have a plesiomorphic radula type with a central, round tooth that has pointed cusps. The bursa copulatrix does not extend beyond the ovarium, which can be a synapomorphic characteristic for this group. Thirdly, Pincerna and Stomacosmethis are both characterised by having a very short tube and the elevated spire and inhabit a largely overlapping geographical area. However, the genital traits of the single known Pincerna and Stomacosmethis species are strikingly different, and the radula of Stomacosmethis with an elongated central tooth and few cusps is unique among Alycaeidae. Thus, dependable grouping of the recognised alycaeid genera is not yet possible because the morphology of radula and genital system, and DNA sequences have been available only in a limited number of alycaeid species. Molecular phylogeny could be a powerful tool to obtain testable hypotheses of evolutionary relationships between species and/or higher taxa. In our attempts, direct PCR amplification of DNA extracted from Alycaeidae snails was not sufficiently successful as that from other families (Junn Kitt Foon, pers. comm.), although few alycaeid taxa have been included in preceding studies (Webster et al. 2012;Hendricks et al. 2019). Conventionally used primers may need to be specifically modified for several key alycaeids to resolve the generic phylogeny of this family. Our analysis of generic relationships including the outcome of molecular phylogeny without Dioryx suggests that the genus Alycaeus is distant from Stomacosmethis and Pincerna, which are closely related and may not be mutually monophyletic. Chamalycaeus, Metalycaeus and Dicharax are also close relatives of one another within the family Alycaeidae (Páll-Gergely et al. in prep.).

Biogeography and fossil records
The Alycaeidae is a characteristic family of the Oriental Biogeographic Region, with a few genera expanding their distributions to the Sino-Japanese/Palaearctic realms (see Holt et al. 2013) (Fig. 46). Isolated occurrence of alycaeids in the Western Ghats supports a hypothesis that the fauna of that region is mostly of Southeast Asian origin (Raheem et al. 2014, Fred Naggs, pers. comm.).
There are three areas that can be considered as biodiversity centres for this family, namely the southeastern Himalaya, northern Vietnam/southern China, and peninsular Malaysia/Sumatra (Table 5), each inhabited by five genera. The diversity in terms of the number of genera decreases towards the periphery of these areas, e.g., southwestern Himalaya (1 genus), southern India (1 genus), Japan (2 genera), and the Philippines (2 genera). The current classification suggests that alycaeids expanded their distributions to Japan and the Philippines in two independent events (Páll-Gergely and Auffenberg 2019). Budha et al. (2015) (and also Kuznetsov 1996 andKuznetsov andSchileyko 1997) reported several alycaeid species from Nepal, but these were not examined by us. Identification of alycaeids is only possible by careful comparison with the type material, which was not done in these studies. Thus, we did not include their identification data in Nepal.
Although Japan is not rich in the number of genera, unique features of conchology are found in a few of the Japanese species, such as the extremely expanded aperture of D. expanstoma, detached initial whorls of D. miyazakii, and uniquely shaped peristome with weak parietal callus in D. okamurai. The genus Pincerna has a conspicuously disjunct distribution. One set of species inhabits the Himalaya, northern Thailand, northern Laos, northern Vietnam, and southern China, whereas the other inhabits peninsular Malaysia, Sumatra, and Borneo.
The only fossil alycaeid is 23-21 million years old Dicharax (?) sonlaensis (see Raheem and Schneider 2018) from northern Vietnam, which fits the range of morphological variation of an extant Dicharax species of the same region. In recent years several terrestrial caenogastropods were described from 99 million year-old Burmese ambers, and there is more to come. All cyclophoroidean families of Southeast Asia (Cyclophoridae, Diplommatinidae, Pupinidae) have been found from mid-Cretaceous Burmese amber (Hirano et al. 2019;Neubauer et al. 2019) with the exception of the Alycaeidae. The absence of alycaeids in Burmese amber may suggest that this is a younger group than the other related families, which is in agreement with the molecular dating of Hirano et al. (2019). Nevertheless, special attention should be paid on alycaeid-like fossil shells since they would not be recognised as alycaeids without the sutural tube and the R2 region that is differently ribbed than the other parts of the body whorl. This study was supported by the MTA (Hungarian Academy of Sciences) Premium Post Doctorate Research Program and the SYNTHESYS Project (GB-TAF-2523) for BP-G, and by Grants-in-Aid for Scientific Research (KAKENHI) from Japan Society for the Promotion of Science to TA. SS and BT are grateful to the Director of the Zoological Survey of India, Kolkata for providing the necessary facilities for this study. We are indebted to The Biodiversity Heritage Library for the multitude of rare literature made available to us (www.biodiversitylibrary.org).