Streptaxis discus Pfeiffer, 1853, by subsequent designation by Ancey (1884: 399).

Shell flattened to globose-heliciform. Last whorl rounded to angular, less distorted, and often with peripheral keel; whorls regularly to rapidly expanded. Apertural dentition varied, ranging from only one parietal lamella to additional dentition: upper palatal, palatal, basal, columellar and supracolumellar lamellae. Genitalia with short to long penis, sometimes with penial appendix and penial sheath covering entire penis length. Penial hooks present and vaginal hook absent.

This genus was recently revised in both shell and genital diagnostic characters, and the intrageneric relationship was discussed (Siriboon et al. 2014a, 2020). At present, the genus Discartemon comprises thirty recognized species, including a new species described herein (Sutcharit et al. 2020).

Holotype CUMZ 5108; paratypes CUMZ 5107 (14 shells), CUMZ 5101 (30 shells), CUMZ 5102 (25 shells), CUMZ 5104 (18 shells), CUMZ 5105 (30 shells), CUMZ 5106 (20 juvenile shells). Limestone outcrop ~ 3.4 km south of the Phra (Buddha) Cave, Lenya National Park, Tanintharyi Township, Tanintharyi Region, Myanmar (11°11'56.2"N, 99°10'25.7"E): CUMZ 13001 (7 specimens in ethanol; Fig. 3A, B).

Figure 2. 

Living snails A Discartemon tonywhitteni from near Phra (Buddha) Cave, Tanintharyi Region (shell width ~ 10 mm) B Discartemon paurodeviatus sp. nov. from the type locality (shell width ~ 11 mm) C Haploptychius heliakosus sp. nov. from the type locality (shell height ~ 9 mm) D Carinartemis exacutus from Lun Nga Mountain, Kayin State (shell height ~ 14 mm) E, F Carinartemis sankeyi (E) from Kayon Cave, Mon State (shell height ~ 10 mm) and (F) from Saddan Cave, Mawlamyine, Mon State (shell height ~10 mm).

Figure 3. 

A, B Discartemon tonywhitteni, specimen CUMZ 6264 from Phra (Buddha) Cave, Tanintharyi Region C–E Discartemon paurodeviatus sp. nov. C holotype CUMZ 13002 with apertural dentition and D, E paratypes CUMZ 13003 from the type locality.

This species was clearly described in Sutcharit et al. (2020). Shell is depressed-heliciform, white and translucent, spire low conical to convex with wide and depressed suture. Shell surface glossy, with fine transverse ridges that diminish below periphery; varices present. Embryonic shell large, ~ 2½ whorls with smooth surface; following whorls in regularly expanding coil. Last whorl usually angular; widely open umbilicus. Apertural dentition with one strong parietal, one palatal, one basal, one columellar and one supracolumellar lamella (Fig. 3A, B).

Genital organs. Atrium (at) short. Penis (p) long and slender. Penial sheath (ps) thin and extending ~1/2 to 3/4 of penis length; penial sheath retractor muscle (psr) very thin, originating at atrium and inserting distally on penial sheath (Fig. 4A). Vas deferens (vd) very short, ~ 1/6 of penial sheath length and passes through penial sheath before entering penis distally (Fig. 4B). Penial retractor muscle (pr) thin and very long, inserting at penis and vas deferens junction.

Figure 4. 

Genital anatomy of A, B Discartemon tonywhitteni, specimen CUMZ 13001 A reproductive system and B insertion of vas deferens into penial sheath C, D Discartemon paurodeviatus sp. nov., paratype CUMZ 13003 C reproductive system and D insertion of vas deferens into penial sheath.

Internal wall of atrium generally smooth (Fig. 5A). Proximal and middle penial wall with dense and translucent penial hooks (~ 5 hooks/200 μm²) and located on conical papillae (Fig. 5B–D). Penial hooks small (<0.04 mm in length), expanded at base, tips pointed (Fig. 5C, E). and curved towards genital orifice. Most penial hooks with blunt tips (Fig. 5E). Distal penial wall with dense and translucent conical penial papillae with embedded penial hooks, ~ 12 penial papillae/200 μm² (Fig. 5F).

Figure 5. 

Internal sculpture of genitalia of Discartemon tonywhitteni, specimen CUMZ 13001 A atrium surface B arrangement of penial hooks on proximal part of penis C lateral view of proximal penial hooks D arrangement of penial hooks on middle part of penis E high magnification view of pointed penial hooks on middle part of penis F top view of distal penial hooks embedded in penial papillae G arrangement of transverse vaginal folds.

Vagina (v) short, ~ 1/3 of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Free oviduct (fo) long, ~ 2 times of vagina length. Oviduct (ov) slender and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club shaped. Hermaphroditic duct (hd) bearing long seminal vesicle (sv) ca. twice as long as the length from talon to branching point of seminal vesicle (Fig. 4A).

Vaginal wall with transverse vaginal folds; vaginal hook absent (Fig. 5G).

Radula. Each row consists of ~ 35‒49 teeth with formula (24‒17) ‒1‒ (17‒24). Central tooth very small with pointed cusp. Lateral and marginal teeth undifferentiated, unicuspid and lanceolate. Latero-marginal teeth gradually reducing in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24A).

Discartemon tonywhitteni is the southernmost distributed species and, currently, is known as the only form from the type locality (Fig. 1), which is an isolated limestone outcrop in Tanintharyi Region, southern Myanmar (Sutcharit et al. 2020).

Sutcharit et al. (2020) described D. tonywhitteni based only on shells. Fortunately, seven alcohol-preserved specimens collected near the type locality were sent by the FFI staff after the species was published. These additional specimens allow us to describe the genitalia and radular morphology of this species herein.

Holotype CUMZ 13002 (Fig. 3C). Measurements: shell height 7.6 mm, shell width 11.0 mm, and 6 whorls. Paratypes CUMZ 13003 (14 shells; Fig. 3D, E), CUMZ 13004 (3 specimens in ethanol), NHMUK (2 shells), all from the type locality.

Small hill on Pahtaw Pahtet Island (~ 500 m west of Myeik Town), Myeik Township, Tanintharyi Region, Myanmar (12°26'3.5"N, 98°35'14.1"E).

Discartemon paurodeviatus sp. nov. can be distinguished from D. collingei (Sykes, 1902) from Malaysia by having a larger shell, rounded last whorl, semi-ovate and slightly reflected aperture, and sometimes supracollumellar lamellae are present. Compared with D. vandermeermohri van Benthem Jutting, 1959 and D. mekalostraka Siriboon & Panha, 2014 from Thailand, this new species has a slightly extended last whorl from the penultimate whorl, last whorl slightly axially deflected, widely open umbilicus, and semi-ovate aperture. The genital organs of D. paurodeviatus sp. nov. differ from D. mekalostraka by having corrugated atrium without pore, short penis, dense brownish and long slender penial hooks located on penial papillae, and short vagina with thickened and reticulated vaginal folds.

Shell globose-heliciform, white and translucent; whorls 6–6½; spire conical with distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery; varices present. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Last whorl rounded, little axially deflected and extruded from the penultimate whorl. Aperture semi-ovate; peristome yellowish to whitish, discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal, one small palatal, one large basal, and one small columellar lamella; sometimes with small supracolumellar lamellae. Umbilicus open and deep (Fig. 3C–E).

Genital organs. Atrium (at) short. Penis (p) long and slender. Penial sheath (ps) very thin, extending entire penis length; penial sheath retractor muscle (psr) very thin, originating at atrium and inserting distally on penial sheath (Fig. 4C). Vas deferens (vd) passes through penial sheath without insertion before entering penis distally (Fig. 4D). Penial retractor muscle (pr) thin and long, inserting at penis and vas deferens junction.

Internal wall of atrium corrugated with sparse atrial pores (Fig. 6A). Penial wall with scattered, very long, slender, and pale brown penial hooks (~ 10 hooks/200 μm²), hooks located on conical papillae that are separated by distinct reticulated folds (Fig. 6C, D). Penial hooks of small size (< 0.08 mm in length), slightly expanded and conical at base, tip sharp and directed towards genital orifice (Fig. 6B, E, F).

Figure 6. 

Internal sculpture of genitalia of Discartemon paurodeviatus sp. nov., paratype 13003 A junction of atrium, vagina, and proximal penis B, C lateral view of penial hooks on proximal part of penis D reticulated arrangement of penial hooks on middle part of penis E lateral view of penial hooks F arrangement of penial hooks on distal part of penis G arrangement of thickened reticulated vaginal folds.

Vagina (v) very short and stout, ~ 1/7 of penis length. Gametolytic duct (gd) a long and slender tube extending as far as albumin gland; gametolytic sac (gs) ovate. Proximal free oviduct (fo) convoluted and distally long and thick, ~ 3 times of vagina length. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club shaped. Hermaphroditic duct (hd) bearing short and thickened seminal vesicle (sv) and ca. same length as from talon to branching point of seminal vesicle (Fig. 4C).

Vaginal wall generally with thickened reticulated vaginal folds, smooth surface, and vaginal pores present (Fig. 6A, G).

Radula. Each row consists of ~ 21‒33 teeth with formula (16‒10)‒1‒(10‒16). Central tooth small with pointed cusp. Lateral and marginal teeth largest and undifferentiated, unicuspidal, and lanceolate. Latero-marginal teeth rapidly reducing in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24B).

The specific name paurodeviatus is derived from the Greek word pauros meaning little or few and the Latin word devius meaning out of the way. It refers to the last whorl of the new species as being slightly axially deflected and extruded from the penultimate whorl.

The species is only known from the type locality in southern Myanmar (Fig. 1).

Variation occurs in the possession of supracolumellar lamellae in some specimens. Currently, two species of Discartemon (D. paurodeviatus sp. nov. and D. tonywhitteni) have been recognized from Myanmar (Sutcharit et al. 2020). These two species are noticeably different in shell morphology and internal structure of genitalia and found in distant localities from each other.

Ennea bulbulus Morelet, 1862 by subsequent designation by Kobelt (1906: 101).

Shell globosely ovate to sub-heliciform, translucent to opaque. Penultimate whorl slightly extended beyond last whorl. Last whorl rounded or flattened along the periphery, and axially deflected from penultimate whorl. Aperture oblique-ovate to squarish; apertural dentition with parietal (one or two), palatal, basal, and columellar lamellae. Genitalia with penial sheath covering ~ 1/2 of penis length, and penial hook present.

The genus Oophana shares the ovate shell shape with the Haploptychius. However, Oophana can be distinguished by generally having a greater number of apertural dentitions (parietal, palatal, basal and columellar lamellae), while Haploptychius has only one parietal lamella (Schileyko 2000; Inkhavilay et al. 2016).

Generally, despite Oophana and Indoartemon Forcart, 1946 possessing an ovate shell with a blunt spire, the former can be distinguished by its parietal, palatal, basal, and columellar lamellae, while the latter possesses only one parietal and one palatal lamella (Schileyko 2000; Siriboon et al. 2014a). Oophana can be distinguished from Discartemon and Perrottetia Kobelt, 1905 by its globosely ovate shell, axially deflected last whorl, and penultimate whorl more or less extended from the last whorl. In comparison, Discartemon has a flattened to a globose-heliciform shell, regularly to rapidly growing last whorl that is less deflected, and penultimate whorl does not extend from the last whorl (Siriboon et al. 2014a). Perrottetia possesses a sub-heliciform and depressed shell, with longitudinal furrows behind the apertural lip, and a less deflected last whorl (Siriboon et al. 2013; Inkhavilay et al. 2016). Moreover, Oophana can easily be separated from the Carinartemis Siriboon & Panha, 2014 by their rounded penultimate whorl with more apertural dentition, whereas the latter genus has a sharply keeled penultimate whorl, and without or with only one parietal lamella (Siriboon et al. 2014b).

Generally, Oophana shows high variability in shell form, and apertural dentition with upper palatal and supracolumellar lamellae occurring in some species (Siriboon et al. 2020). However, examination of the genitalia in most species including the type species is still limited, making comparisons with other congeners difficult.

The phylogenetic relationships of the Oophana s.l. from Thailand were recently shown to be polyphyletic and comprised of three groups. These polyphyletic groups could possibly be recognized as distinct genera supported by their unique shell and genital characters (Siriboon et al. 2020). Furthermore, the oblique-heliciform shell and apertural dentition with four lamellae are shared among these three polyphyletic groups. Nevertheless, without the information on the type species, these characters are insufficient to restrict the true Oophana s.s., and so, in this revision we place the streptaxids that have an oblique-ovate shell and apertural dentition with four lamellae within the genus Oophana s.l.

The shell is oblique-heliciform with convex spire and a distinct suture. Whorls 7 and shell surface with transverse ridges that diminish below the periphery. Shell periphery is keeled, and last whorl axially deflected. Umbilicus open and deep. Aperture is subquadrangular, peristome reflected. Apertural dentition with one parietal, one basal, two weak palatal, and one columellar lamella.

This species is known only from the type locality, in the southern part of Myanmar. No fresh materials were collected in this survey. Herein, the description of this species is based only on the original description. Gould (1856) received the specimen from Rev. J. Benjamin and described it without providing any figures. In the description, Gould compared O. elisa with two species: Seychellaxis souleyetianus (Petit, 1841) and Haploptychius pyriformis (Pfeiffer in Philippi, 1845). In differentiating the three, Gould noted that O. elisa has a larger and a more depressed shell than S. souleyetianus, and that O. elisa has a more elongated shell that is two-fold larger in size and posterior denticle (presumably parietal lamella) smaller than H. pyriformis. Based on this comparison, we assume that the shell of O. elisa differs from all other known congeners from Myanmar and Peninsular Malaysia by its largely deflected last whorl, discoid spire and keeled penultimate whorl. Besides probably having the same distribution range, O. elisa is similar to D. paurodeviatus sp. nov. in having a quite straight and parallel aperture lip, and four apertural dentitions. However, O. elisa seems to have an oblique-ovate shell with more deflected last whorl, keeled penultimate whorl, and discoid spire. Meanwhile, D. paurodeviatus sp. nov. possesses a globose shell with less deflected last whorl, and penultimate whorls being rounded. To date, no specimens or illustrations have been found after the first record.

Possible syntype NHMUK ex. Cuming collection (3 shells; Fig. 7A) from Camboja [Cambodia]. NHMUK ex. Cuming collection (2 shells) from Siam. Phra (Buddha) Cave, Tanintharyi Region, Myanmar (11°14'01.5"N, 99°10'42.8"E): CUMZ 13005 (1 shell; Fig. 7B).

Figure 7. 

A, B Oophana mouhoti A possible syntype NHMUK ex. Cuming collection from Camboja and B specimen CUMZ 13005 from Phra (Buddha) Cave, Tanintharyi C, D Oophana obtusus C specimen NHMUK 1888.12.4.788–790 from Chauktalon, Moulmein with apertural dentition and D specimen NHMUK 1871.9.23.64 from Moulmein E Oophana laevis, possible syntype NHMUK 1899.7.4.11 from Burma.

Oophana mouhoti can be distinguished from O. obtusus (Stoliczka, 1871) by its higher spire, expanded aperture lip, deflected last whorl, and slightly angulate penultimate whorl. In contrast, O. obtusus exhibits a narrow aperture, spire convex, periphery of penultimate whorl usually equal to last whorl, strong columellar lamella, and small tubercle near the posterior angle of aperture.

Shell oblique-ovate, white, and translucent; whorls 6½; spire elevated conical with distinct suture. Shell surface glossy with fine transverse ridges that diminish below the periphery; following whorls regularly coiled. Shell periphery rounded and last whorl axially deflected. Aperture subcircular; peristome expanded, thickened, discontinuous, and reflected. Apertural dentition with one strong parietal, one small upper palatal, one small palatal, and one basal lamella. Umbilicus open and deep (Fig. 7A, B).

This species has been recorded from several localities in Peninsular Thailand (Siriboon et al. 2020) along the southeastern part of the Tenasserim Range. However, only one specimen was collected in Myanmar from the Tanintharyi Region.

The only shell was collected from the limestone hills at Buddha Cave, Tanintharyi Region; it matches well with this species.

Oophana mouhoti was originally described based on specimens in the collection of H. Cuming with the very brief collection locality given as Siam. The NHM, London holds a lot of three specimens in the Cuming collection collected by H. Mouhot but has Camboja as the collection locality. This specimen lot does not have Pfeiffer’ handwriting on the label; therefore, they are considered possible syntypes. However, Mouhot’s recorded localities were generally imprecise. No additional specimens for this species are available, nor are records or literature references from Cambodia, other than peninsular Thailand (Sutcharit et al. 2020). A similar situation of imprecise type locality records with Mouhot-collected specimens have been clarified in the case of helicarionid species (see Pholyotha et al. 2020). The recent works on land snails from Thailand confirmed that the specimens from the limestone hills along peninsular Thailand identified as O. mouhoti match well with the possible syntype. Therefore, peninsular Thailand (Petchaburi and Prachuap Khiri Khan provinces) are possibly the collecting locality for this species. Furthermore, H. Mouhot visited Petchaburi Province once from May to August in 1860 [see travel routes map in Mouhot (1864a, b)]. Additionally, Streptaxis johswichi Martens, 1864 was described based on specimens collected from Petchaburi Province, Thailand. Later, Martens (1867) examined the O. mouhoti specimens in the Cuming collection and agreed that they belonged to the same species.

Moulmein: NHMUK 1903.7.1.4002 (2 shells) ex. Godwin-Austen collection. NHMUK 1871.9.23.64 (1 shell, Fig. 7D). NHMUK 1937.7.91–92. Chauktalon, Moulmein: NHMUK 1906.2.2.342 (3 shells + 1 juvenile) ex. Blanford collection. NHMUK 1888.12.4.788–790 (3 shells, Fig. 7C) ex. Blanford collection. Sacred Lakes, Moulmein: NHMUK 1889.3.15.1 (1 shell) ex. Godwin-Austen collection.

Shell oblique-ovate, white, translucent; whorls 6–7; spire convex with distinct suture. Shell surface glossy with fine transverse ridges, nearly smooth with few transverse ridges near peristome. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl slightly axially deflected. Aperture subcircular; peristome continuous, expanded, slightly reflected, and very short sinulus. Apertural dentition with one strong parietal, one palatal, and one strong columella lamella. Umbilicus open and deep (Fig. 7C, D).

This species is only known from the type locality, the southern part of Myanmar (Stoliczka 1871).

No new specimens were collected in this survey; however, authenticated museum specimens were examined. Regarding genitalia, Oophana obtusus and Haploptychius burmanicus were the first two species anatomically examined and illustrated among several streptaxids in Myanmar by Stoliczka (1871), who noted that there was no noticeable difference in reproductive forms between these two species. Based on the genitalia drawing, O. obtusus has a thick penial sheath covering almost the entire penis, and vas deferens not inserted into the penial sheath, but the lengths of vagina and atrium are unclear. Thus, the description and drawing remain insufficient to confirm the distinguishing characters of this species.

Possible syntype NHMUK 1899.7.4.11 (1 shell; Fig. 7E) ex. Beddome collection from Burma [Myanmar].

Oophana laevis differs from O. mouhoti and O. obtusus by having a rounded penultimate whorl, convex spire, and apertural dentition with parietal and basal lamellae. Although O. mouhoti and O. obtusus have a slightly angular penultimate whorl and elevated spire, O. mouhoti usually has only a parietal lamella (sometimes with basal lamella). In contrast, O. obtusus has parietal, palatal, and columellar lamellae.

Shell oblique-heliciform, white, and translucent; whorls 5½; spire low convex with distinct suture. Shell surface glossy with transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture subquadrangular with sinulus; peristome discontinuous, thin, expanded and reflected. Apertural dentition with one parietal and one basal lamella, and sometimes columellar lamella is absent. Umbilicus open and shallow (Fig. 7E).

This species is known only from the type locality, which was mentioned only as ‘Tenasserim’ (Blandford 1899). This locality possibly refers to the Tanintharyi Region, southeastern Myanmar.

No new specimens were collected in this study. However, we compared the possible type specimen with the other congeners. Blanford (1899) clearly stated that the type series was collected by Beddome and consisted of three specimens. However, the NHM, London holds a lot of only a single specimen from the Beddome collection, with the word India, probably added at a later date, on the label. Therefore, we consider this lot to be a possible syntype.

Helix perrotteti Petit, 1841 by subsequent designation by Forcart (1946: 215).

Shell oblique-heliciform, and translucent. Longitudinal furrows present behind apertural lip. Apertural dentition usually consists of two parietal, one palatal, one basal and one columellar lamella, and upper palatal and supracolumellar lamellae may be present. Genitalia with long and slender penis, penial sheath thin and not extending the entire penis length. Penial hooks dense, pale brown, expanded at base, with pointed tips, located on penial papillae, and curved towards genital orifice. Vaginal hooks may be present.

Perrotettia and Discartemon are generally similar in having complex apertural dentition; however, their shell morphology is obviously different. Perrottetia has a sub-heliciform shell, smaller size, last whorl rounded and more or less deflected, and mostly with two parietal lamellae. Although parietal, palatal, basal and columellar lamellae are always present in Perrottetia, possession of second parietal, upper palatal and supracolumellar lamellae is variable, as is the presence of bifid lamellae (Siriboon et al. 2013; Inkhavilay et al. 2016; Bui et al. 2019). In contrast, Discartemon exhibits flattened to globose-heliciform shells, last whorl rounded to angular and less deflected with, usually, one parietal lamella.

Nonetheless, some Discartemon species from Thailand have two parietal lamellae, for example, D. afthonodontia (see Siriboon et al. 2014a: fig. 7a, b) and D. flavacandida (see Siriboon et al. 2014a: fig. 7e, f). Likewise, some Perrottetia species are also described with only a single parietal lamella, for example, the Vietnamese species P. aberrata (Souleyet, 1852) and P. namdongensis Bui & Do, 2019 (see Bui et al. 2019: figs 2c–e, 3a–c), and the Laos species P. unidentata Inkhavilay & Panha, 2016 (see Inkhavilay et al. 2016: fig. 5f–i).

At present, the genus Perrottetia is comprised of about 30 nominal species distributed from India and Sri Lanka to Indochina and southern China (Kobelt 1906; Richardson 1988; Schileyko 2011; Siriboon et al. 2013; Inkhavilay et al. 2016). So far, P. theobaldi Benson, 1859 is the only species known from Myanmar.

Syntype UMZC I.102535 (2 shells) from unknown locality. Khasi Hill: NHMUK 1888.12.4.784–786 (3 shells; Fig. 8A) ex. Theobald collection. Siam boundary: NHMUK 1903.7.1.4005 (7 shells + 1 juvenile; Fig. 8C) ex. Godwin-Austen collection. Burma: NHMUK 1871.9.23.143 (1 shell; Fig. 8B). Aik Kham Cave, Taunggyi Township, Shan State, Myanmar (20°49'07.0"N, 97°13'42.0"E): CUMZ 13006 (4 shells; Fig. 8D).

Figure 8. 

Perrottetia theobaldi A syntype UMZC I.102535 (no locality data) with apertural dentition B specimen NHMUK 1871.9.23.143 from Burma C specimen NHMUK 1903.7.1.4005 from Siam boundary D specimen CUMZ 13006 from Aik Kham Cave, Taunggyi, Shan State with apertural dentition.

Perrottetia theobaldi is similar to P. dugasti (Morlet, 1892) from Vietnam; however, the former species can be distinguished by having a second parietal lamella running to the main parietal lamella, thicker and less reflected peristome, subquadrangular aperture, and shallow suture. In contrast, P. dugasti has a weak second parietal lamella running to the sinulus, thinner and more reflected peristome, semi-ovate aperture, and a deeper suture with a clear bifid columellar lamella. Similarly, P. mabillei (Bavay & Dautzenberg, 1903) from Vietnam can be separated from P. theobaldi by its strong radial ridges, wide and short sinulus, basal lamella absent, bifid columellar lamellae, and deep umbilicus, while P. theobaldi has a smooth shell surface, long and narrow sinulus, strong basal lamella, columellar lamellae separated, and shallow umbilicus. Furthermore, P. theobaldi differs from the Thai species P. aquilonaria Siriboon & Panha, 2013 by having a shallow suture, narrow and long sinulus, rounded last whorl, peristome thicker and less reflected, aperture subquadrangular and columellar lamellae are separated. In contrast, P. aquilonaria possesses deep suture, shorter and wider sinulus, the last whorl shouldered, aperture subcircular, more expanded peristome, and bifid columellar lamella.

Shell sub-oblique heliciform, white, and translucent; whorls 5–5½; spire convex with distinct suture. Shell surface glossy with transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected; two deep and short longitudinal furrows present. Aperture triangular with sinulus; peristome continuous, thickened, expanded, and reflected. Apertural dentition with one large and strong parietal, nearly adjoined small second parietal lamella; adjoined at right angles, one small upper palatal, one strong palatal, one strong basal, and bifid columellar lamella. Columellar lamella is sometimes absent. Umbilicus narrow (Fig. 8).

This species has been widely recorded from India to Bhutan and Myanmar (Blanford and Godwin-Austen 1908; Ramakrishna et al. 2010; Gittenberger et al. 2021). In Myanmar, the previous record was from Bhamo, Kachin State (Blanford and Godwin-Austin 1908) and the empty shells together with H. thebawi (Godwin-Austin, 1888) were found from Shan State in this sampling.

All the specimens of P. theobaldi (Fig. 8) showed slight differences in the apertural dentition and peristome positions, particularly the columellar and supracolumellar lamellae that are closer or almost united compared to the specimens from the Aik Kham Cave, Shan State (Fig. 8D). However, all were collected from the same range; we place them as the same species.

Streptaxis sinensis Gould, 1859, by original designation.

Shell oblique-heliciform to ovate and last whorl deflected. Penultimate whorl round to bluntly angular and extended beyond last whorl. Apertural dentition includes only one parietal lamella. Genitalia with penial sheath thin to thick and extending ~ 1/2 to entire penis length. Penial hooks dense, slightly expanded at base, tips pointed, located on low to high conical papillae and vaginal hooks absent.

Haploptychius is almost identical with Carinartemis in having a deflected last whorl, extended penultimate whorl, and bearing a single parietal lamella. However, Haploptychius can be recognized by its oblique-ovate shell and rounded to angular penultimate whorl, while Carinartemis possesses an oblique-heliciform shell with sharply keeled penultimate whorl. In genitalia, Haploptychius has long and slender penial hooks, without vaginal hooks, while Carinartemis possesses shorter and blunt penial hooks, and sometimes transparent vaginal hooks may be present (Siriboon et al. 2014b; Inkhavilay et al. 2016).

A recent molecular phylogeny revealed that Haploptychius is polyphyletic, and the traditional genus concept using shell shape and apertural dentition seems unreliable (Siriboon et al. 2020). However, further intensive genital examination and molecular analysis of the type species are necessary to restrict the Haploptychius s.s., and generic revision absolutely requires both forms of evidence. Therefore, since the morphological and molecular evidence have never been evaluated, we follow the traditional genus concept in recognizing the streptaxids with oblique-heliciform shells and only one parietal lamella as members of the genus Haploptychius s.l.

Currently, the genus Haploptychius is comprised of about 40 nominal species distributed from India to Indochina, southern and central China, and Sulawesi of Indonesia (Kobelt 1906; Blanford and Godwin-Austen 1908; Zilch 1961; Richardson 1988; Schileyko 2000; Do and Do 2015; Inkhavilay et al. 2016). In addition, five species of Haploptychius s.l. have been documented mainly in southeastern Myanmar (Blanford and Godwin-Austen 1908), and three new species are added in this study.

Syntype UMZC I.102470 (3 shells; Fig. 9A) from Moulmein. India [error]: NHMUK ex. Cuming collection (1 juvenile). Moulmein: NHMUK 1903.7.1.3990 (4 shells; Fig. 9D) ex. Godwin-Austen collection. NHMUK 1906.2.2.159 (1 juvenile; Fig. 9B) ex. Blanford collection. NHMUK 1906.2.2.340 (2 shells) ex. Blanford collection. NHMUK ex Godwin-Austen collection (2 shells). NHMUK 1888.12.4.768–770 (3 shells; Fig. 9C).

Figure 9. 

Haploptychius bombax A syntype UMZC I.102470 from Moulmein B juvenile specimen NHMUK 1906.2.2.159 from Moulmein C specimen NHMUK 1903.7.1.3990 from Moulmein with apertural dentition D specimen NHMUK 1888.12.4.768–770 from Moulmein with apertural dentition.

Haploptychius bombax can be differentiated from H. burmanicus by having a large oblique-ovate shell, without sinulus, and larger or wider last whorl. In contrast, H. burmanicus possesses a small sub-oblique heliciform shell, wide sinulus, and compressed last whorl. Compared with H. pellucens (Pfeiffer, 1863) from Laos, H. bombax differs by having strong radial ridges, convex spire, and narrow umbilicus, while H. pellucens exhibits a nearly smooth surface, more ovate shape, elevated spire, and umbilicus widely open.

Shell oblique-ovate, white, and translucent; whorls 5½–7; spire convex with distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery of penultimate whorl. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture semi-ovate; peristome discontinuous, thickened, slightly expanded, and reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Fig. 9).

Haploptychius bombax is only known from the type locality in southeastern Myanmar (Benson 1859b).

The original description mentioned only 5½ whorls, but the museum specimen (Fig. 9C, D) had 7 whorls. This study collected no specimens, but authenticated museum specimens (juveniles and adults) were examined.

Syntype NHMUK 1888.12.4.777–779 (3 shells; Fig. 10A) from Pegu.NHMUK 1909.3.15.71 (1 shell; Fig. 10C) ex. Godwin-Austen collection. Pegu, Arakan: NHMUK 1909.3.15.93 (3 shells) ex. H. Blanford collection. Akouktoung, Pegu: NHMUK 1906.2.2.338 (4 shells; Fig. 10B) ex. W.T. Blanford collection. Pegu, Arakan: NHMUK 1909.3.15.93 (3 shells) ex. H. Blanford collection.

Figure 10. 

A–C Haploptychius blanfordi A syntype NHMUK 1888.12.4.777–779 from Pegu with apertural dentition B specimen NHMUK 1906.2.2.338 from Akouktoung, Pegu C specimen NHMUK 1909.3.15.71 from Pegu D Haploptychius burmanicus, syntype NHMUK 1906.2.2.199 from Tongoop, Arakan with apertural dentition.

Haploptychius fischeri (Morlet, 1887) almost shares the same shell form as H. blanfordi, but the latter possesses a more depressed shell, penultimate whorl more bulging, aperture wider, longer and subquadrangular shape.

Shell oblique-heliciform, white, and translucent; whorls 6; spire convex with distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture semi-ovate; peristome discontinuous, thickened, expanded, and reflected. Apertural dentition with one strong parietal and small palatal lamellae. Umbilicus open and deep (Fig. 10A–C).

This species has been recorded with a wide distribution range from Arakan [Rakhine State], Pegu [Bago Region], and Shan State in Myanmar. However, the record from Cocos Islands in the southern Indian Ocean by Blanford and Godwin-Austen (1908) needs to be verified with modern evidence rather than by shell morphology alone.

The taxonomic status of this species is still ambiguous because it is identical in shell morphology to Streptaxis birmanica. Theobald (1864) consecutively described Streptaxis blanfordi and Streptaxis birmanica based on specimens from the same geographical area as Pegu. These two nominal species resemble each other in having one parietal and one palatal lamella, whereas they differ in only minor characters of shell shape and size. In this revision, we consider these two nominal species as synonyms. Only the type specimens of H. blanfordi could be located and examined; we therefore consider Streptaxis birmanica as the junior synonym.

The original spelling of the species was blanfordi, which was intentionally modified to blanfordianus by Stoliczka (1871) but for an unclear reason. This subsequent spelling of blanfordianus is an unjustified emendation made available with its own authorship and date, and so became a junior objective synonym (ICZN 1999: Arts 32.3, 33.2.3, 50.5).

Theobald (1864) clearly stated that Streptaxis birmanica W. Blanford, (in MSS.) was described based on a single specimen received from W.T. Blanford. However, we could not locate this single shell as the holotype fixed by monotypy. Theobald (1864) also stated that the other two shells lacked the palatal lamella and were of a relatively smaller size, which are recognized as distinct varietal entities. Therefore, these two specimens are excluded from the type series of Streptaxis birmanica. The authorship was originally attributed to W.T. Blanford as the manuscript name. However, since Blanford did not write the description or credit the description to W.T. Blanford, the taxon is attributed to Theobald only (ICZN 1999: Art. 50.1.1).

Possible syntype NHMUK 1906.2.2.199 (2 adults + 1 juvenile; Fig. 10D) ex. W.T. Blanford collection from Tongoop, Arakan [Taungup, Rakhine State].

Shell oblique-heliciform, white, and translucent; whorls 6; spire convex with distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture semi-ovate; peristome continuous; sometimes discontinuous, thin, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Fig. 10D).

Haploptychius burmanicus is still known only from the type locality in southern Myanmar (Blanford 1865). Outside Myanmar, it is also reported from Mizoram in India (Ramakrishna et al. 2010); however, this record needs to be verified.

This species highly resembles H. blanfordi in shell form, but H. burmanicus is more globosely heliciform, with a higher spire and only one parietal lamella. Without anatomical information, the generic placement of this species is still tentative, and we retain this as Blanford and Godwin-Austen (1908). In addition, H. perlissus Vermeulen et al. 2019 from Vietnam (Vermeulen et al. 2019: figs 49–51) can be distinguished from H. burmanicus by having an oblique-ovate shell, less extended penultimate whorl from the last whorl, lower to nearly flattened spire, the palatal side is almost straight, basal side rounded, and columellar side broadly rounded, whereas H. burmanicus has a higher spire, more compressed shell, and the last whorl is more axially deflected.

Moulmein: NHMUK 1937.7.9.10 (1 shell). NHMUK 1906.2.2.339 (1 shell) ex. Blanford collection. NHMUK 1888.12.4.774–776 (3 shells; Fig. 11B). NHMUK 1909.3.15.75 (1 shell; Fig. 11A) ex. Godwin-Austen collection. Pathen Mountain, east bank of Attaran River and ~ 45 km southeast of Kyaikmaraw Township, Mawlamyine District, Mon State, Myanmar (16°14'7.5"N, 97°56'48.1"E): CUMZ 13007 (15 shells; Fig. 11C, D).

Figure 11. 

Haploptychius solidulus A specimen NHMUK 1909.3.15.75 from Moulmein with apertural dentition B specimen NHMUK 1888.12.4.774–776 from Molumein C, D specimen CUMZ 13007 from Pathen Mountain, Mawlamyine, Mon State with apertural dentition.

Among the Haploptychius species from Myanmar, this species is distinctly large with an oblique-ovate shell, and less deflected last whorl. Haploptychius solidulus has almost the same shell form as Oophana mouhoti. However, it differs from O. mouhoti by having somewhat enlarged last whorl, more deflected last whorl, and a conical spire with only one parietal lamella. In contrast, O. mouhoti shows a depressed and obtuse conical spire, with one parietal and small basal lamellae.

Shell oblique-ovate, white, and opaque; whorls 6½–7; spire elevated conical with distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture semi-ovate; peristome discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Fig. 11).

This species appears to be restricted to limestone karsts and is only recorded from southern Myanmar.

Stoliczka (1871) mentioned the specimens received from Theobald, who collected at Yethebiankoo [Rathe Pyan Cave] on the Attaran river, south-east of Moulmein [Mawlamyine]. Therefore, the exact type locality is assumed to be Rathe Pyan Cave, but it is located southwest of Hpa-an, Kayin State. Unfortunately, no living specimens could be examined.

Limestone hills (Apache Cement Factory), Pyinyaung Village, Thazi Township, Meiktila District, Mandalay Region, Myanmar (20°49'39.1"N, 96°23'35.1"E): CUMZ 13008 (4 shells; Fig. 12A–C). Ywangan Village, near Lin Way Monastery, Kalaw Township, Taunggyi District, Shan State, Myanmar (21°13'43.3"N, 96°33'19.2"E): CUMZ 13009 (7 shells). Aik Kham Cave, Taunggyi Township, Taunggyi District, Shan State, Myanmar (20°49'07.0"N, 97°13'42.0"E): CUMZ 13010 (3 shells; Fig. 12D, E).

Figure 12. 

Haploptychius thebawi A–C specimens CUMZ13008 from Pyinyaung Village, Meiktila, Mandalay Region, with apertural dentition D, E specimens CUMZ 13010 from Aik Kham Cave, Taunggyi, Shan State.

Haploptychius thebawi is similar to H. solidulus in having a high conical spire and globosely ovate shell. The former species can be discriminated by its smoother shell surface and narrower aperture, more rounded and extended penultimate whorl, and less inflated last whorl. Additionally, H. thebawi resembles H. porrectus (Pfeiffer, 1863) from Laos in having strong radial ridges, conical spire, and an inflated and deflected last whorl, whereas H. thebawi exhibits a larger shell, less depressed and deflected last whorl, fine radial ridges, and higher spire.

Shell oblique-heliciform, white and translucent; whorls 5½–6½; spire conical with distinct suture. Shell surface glossy with transverse ridges that diminish below periphery. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery rounded; last whorl axially deflected. Aperture subcircular; peristome discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Fig. 12).

This species occurs in central-eastern Myanmar, based on the type locality and two localities in Shan State, one locality in Mandalay Region, and it is relatively low in population density.

Originally, H. thebawi was described based on specimens from Pingoung, Shan Hills, which is probably now referred to as Pinlaung Township, Taunggyi District, Shan State. Unfortunately, the type specimens of H. thebawi could not be located in the NHM, London collection. However, the specimens examined herein match well with the original description and the syntype illustrated in Gude (1903: figs 11–13). Despite that, the specimens from Mandalay Region tend to have a more ovate shell and elongated last whorl, and their smooth shell surface, narrow umbilicus, and conical spire make them most similar to this nominal species. Therefore, we treat this population as an intraspecific variation. Examination of genitalia of specimens from this population is necessary to clarify their taxonomic status.

Blanford and Godwin-Austen (1908) treated this nominal species as a junior synonym of H. burmanicus. However, the recently collected specimens of H. thebawi can be distinguished from H. burmanicus and H. blanfordi by having an oblique-ovate to oblique-heliciform shell, elevated and conical spire, nearly smooth shell surface, penultimate whorl extended beyond last whorl, only one parietal lamella, and narrow umbilicus. Conversely, the two latter species have sub-oblique heliciform shells, depressed spire, prominent radial ridges on the shell surface, penultimate whorl slightly extended beyond the last whorl, with one parietal and one palatal lamella, and a wide umbilicus. Therefore, we consider H. thebawi to stand as a separate species.

Among three populations of H. thebawi (Table 1), Aik Kham Cave specimens have the smallest size with a more depressed shell, followed by Ywangan Village; Apache Cement Factory specimens have the largest shell with more conical spire and rounded last whorl.

Holotype CUMZ 13011 (Fig. 13A). Measurements: shell height 4.5 mm, shell width 8.6 mm, and 6 whorls. Paratypes CUMZ 13012 (5 shells; Fig. 13B, C), NHMUK (2 shells).

Figure 13. 

A–C Haploptychius tenasserimicus sp. nov. A holotype CUMZ 13011 with apertural dentition B, C paratypes CUMZ 13012 from the type locality D Haploptychius heliakosus sp. nov. holotype CUMZ 13013 with apertural dentition.

This new species was found from the limestone karsts near Lampane Village, Tanintharyi Region, Myanmar (11°40'18.1"N, 99°13'30.1"E).

The specific name tenasserimicus refers to the type locality of this new species located on the Tenasserim Mountain Range, which forms the backbone of Indochina.

This species is distinguishable by its small size, angular penultimate whorl, low convex spire, and aperture that elongates and grows almost horizontally. Haploptychius tenasserimicus sp. nov. differs from H. burmanicus and H. blanfordi species by having oblique-ovate shells, prominent transverse ridges, higher spire, rounded penultimate whorl, and less deflected last whorl. This new species also differs from H. blaisei (Dautzenberg & Fischer, 1905) from Laos and Vietnam by having a relatively smaller shell (width ~ 8 mm), nearly flattened spire, angular penultimate whorl and rounded last whorl. In contrast, H. blaisei possesses a relatively larger shell (width ~ 10 mm), higher spire, rounded penultimate whorl, and compressed last whorl. In addition, H. tenasserimicus sp. nov. can be distinguished from H. dorri (Dautzenberg, 1894) from Vietnam (see Inkhavilay et al. 2016) by having a more depressed and larger shell (width ~ 8 mm), angular penultimate whorl, aperture longer and more axially deflected last whorl. Haplotychius dorri exhibits a depressed and smaller shell (width ~ 5 mm), smooth shell surface, rounded penultimate whorl, shorter aperture and last whorl less axially deflected from the vertical axis.

Shell sub-oblique heliciform, white and translucent; whorls 6; spire low convex with distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery; varices present. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery angular; last whorl axially deflected. Aperture semi-ovate; peristome discontinuous, expanded and slightly reflected. Apertural dentition with one parietal lamella. Umbilicus open and shallow (Fig. 13A–C).

This species was only collected from the type locality; limestone hills in primary forest in the Tanintharyi Region, Myanmar.

The genitalia information is not known.

Holotype CUMZ 13013 (Fig. 13D). Measurements: shell height 9.0 mm, shell width 10.2 mm, and 7 whorls. Paratypes CUMZ 13014 (24 shells; Fig. 14A), CUMZ 13015 (15 specimens in ethanol), NHMUK (2 shells).

Figure 14. 

A, B Haploptychius heliakosus sp. nov. A paratype CUMZ 13014 from the type locality and B specimen CUMZ 13016 from Kyonknow Cave, Hpa-an, Kayin State C–E Haploptychius karenorum sp. nov. C holotype CUMZ 13017 with apertural dentition D paratype CUMZ 13018 from the type locality and E specimen CUMZ 13019 from Taung Lay Cave, Hpa-an, Kayin State.

Bardai Mountain, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°59'50"N, 97°41'48"E).

Kyonknow Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (17°01'00.1"N, 97°41'42.1"E): CUMZ 13016 (7 shells; Fig. 14B).

Haplotychius heliakosus sp. nov. differs from H. bombax by having a deeper suture, higher spire, rounded penultimate whorl, and subquadrangular aperture. In contrast, H. bombax possesses a relatively shallower suture, lower spire, angular penultimate whorl, and semi-ovate aperture. Haplotychius heliakosus sp. nov. also differs from H. burmanicus and H. blanfordi by having an oblique ovate shell, higher spire, and less axially deflected last whorl. In contrast, the two latter species exhibit a depressed heliciform shell and lower spire, and more axially deflected last whorl. Although H. heliakosus sp. nov. has a shell similar to H. pellucens from Laos, this new species has a less axially reflected last whorl, subquadrangular aperture, and more ridges on the shell surface. Additionally, the genitalia of H. heliakosus sp. nov. has a thickened penial sheath covering almost the entire penis, and short and stout penial hooks on papillae, while H. pellucens has a thin penial sheath covering ~ 1/2 of the penis, and long and slender penial hooks without papillae. This new species differs from C. exacutus (Gould, 1856) by having penial sheath retractor muscle originating at atrium, vas deferens passing through a short section of thin penial sheath before extending ~ 1/3 of the penial sheath length to the curved portion, shorter free oviduct, seminal vesicle ca. twice the length from talon to branching point of seminal vesicle, thickened atrial folds with sparse atrial pores, and stout distal penial hooks.

Shell oblique-ovate, white, and translucent; whorls 7–7½; spire low conical with distinct suture. Shell surface glossy with transverse ridge, nearly smooth with few transverse ridges near peristome. Embryonic shell large, ~ 2½ whorls with smooth surface; following whorls regularly coiled. Penultimate whorl rounded; last whorl axially deflected. Aperture subquadrangular; peristome discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella and sometimes with small second parietal lamella adjoined at a right angle. Umbilicus open and deep (Fig. 13D, 14A, B).

Genital organs. Atrium (at) short. Penis (p) very thin, and long tube. Penial sheath (ps) muscularly enlarged, very thickened, and extending entire penis length; penial sheath retractor muscle (psr) thin, originating at atrium, and inserting distally on penial sheath (Fig. 15A). Vas deferens (vd) passes through a short section of thin penial sheath then extends ~ 1/3 of the penial sheath length to a curved portion before entering penis distally. Curved portion with very thin connective tissue attached between vas deferens and penial sheath wall (Fig. 15B). Penial retractor muscle (pr) thin, very long, inserting at junction of penis and vas deferens.

Figure 15. 

Genital anatomy of Haploptychius heliakosus sp. nov. paratype CUMZ 13014 A reproductive system B insertion of vas deferens into penial sheath.

Internal wall of atrium generally smooth with transverse thickened atrial folds with sparse atrial pores (Fig. 16A). Proximal penial wall with scattered pale brownish penial hooks, ~ 26 hooks/200 μm²; hooks located on irregular trapezoidal penial papillae and separated by longitudinal folds (Fig. 16B). Penial hooks small (< 0.04 mm in length), slightly expanded at base, tips pointed, and slightly curving away from genital orifice (Fig. 16C). Penial wall on middle to distal parts with scattered light brownish penial hooks, ~ 24 hooks/200 μm²; hooks located on laterally-flattened penial papillae separated by longitudinal folds (Fig. 16D, E). Penial hooks short, stout, small (< 0.01 mm in length), expanded at base, tips obtuse and curved towards genital orifice (Fig. 16F–H).

Figure 16. 

Internal sculpture of genitalia of Haploptychius heliakosus sp. nov. paratype CUMZ 13014 A atrium surface B arrangement of penial hooks on proximal part of penis C top view of penial hook D, E arrangement of penial hooks on middle part of penis F top view of penial hook with obtuse tip G arrangement of penial hooks on distal part of penis H high magnification of penial hook with obtuse tip I vaginal folds.

Internal wall of atrium generally smooth with sparse atrial pores (Fig. 23A). Proximal penial wall covered with scattered and pale brownish penial hooks, ~ 12 hooks/200 μm². Proximal penial hooks located on laterally flattened penial papillae; hooks small and short (< 0.03 mm in length), slightly expanded at base, tips obtuse and curved towards genital orifice (Fig. 23B, C). Middle and distal penial walls densely covered with pale brownish hooks, ~ 20 hooks/200 μm². Middle and distal hooks located on laterally compressed penial papillae separated by reticulated folds; hooks small, short (< 0.01 mm in length), slightly expanded at base, tips pointed (Fig. 23D–G).

Vagina very short, stout, and ~ 1/10 of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Proximal free oviduct (fo) enlarged, tapering to a smaller tube in the middle part, then enlarged distally. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short, and club shaped. Hermaphroditic duct (hd) bearing long seminal vesicle (sv) of about twice the length from talon to branching point of seminal vesicle (Fig. 15A).

Vaginal wall with longitudinal vaginal folds (Fig. 16I), folds with nearly smooth surface, and vaginal hook absent.

Radula. Each row consists of ~ 35 teeth with formula (17)–1–(17). Central tooth very small with pointed cusp. Lateral and marginal teeth undifferentiated, lanceolate, unicuspid, and lanceolate. Latero-marginal teeth gradually reduced in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24C).

The specific name heliakosus is derived from the Greek word heliakos meaning of the sun. It honors our colleague, Dr. Arthit Pholyotha, who collected the specimens and took the photos of the living snails used in this study. His first name Arthit means the Sun.

This new species is currently known from two localities in the limestone karsts near Salween (Thanlwin) Basin, Kayin State, southeastern Myanmar.

Shell variations of H. heliakosus sp. nov. were found between two populations. Specimens from the Kyonknow population (Fig. 14B) have a straighter periphery or nearly cylindrical last whorl compared to those from the type locality, Bardai Mountain (Fig. 13D, 14A). As no living specimens from the Kyonknow Cave were collected, we considered the Kyonknow population as an intraspecific variation of H. heliakosus sp. nov. because this locality is very close to the type locality. Living specimens from the Kyonknow population and genital examination are necessary to resolve these systematic issues.

Holotype CUMZ 13017 (Fig. 14C). Measurements: shell height 9 mm, shell width 11.6 mm and 7 whorls. Paratypes CUMZ 13018 (6 shells; Fig. 14D), NHMUK (2 shells).

Limestone outcrops at Waiponla Hill, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°56'7.4"N, 97°42'56.8"E).

Taung Lay Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (17°11'40.3"N, 97°37'47.0"E): CUMZ 13019 (2 shells; Fig. 14E).

Haploptychius karenorum sp. nov. can be differentiated from H. heliakosus sp. nov. by having a convex spire, penultimate whorl angular and extended well beyond the diameter of the last whorl, and more axially deflected last whorl. In contrast, H. heliakosus sp. nov. possesses an elevated spire, penultimate whorl rounded, less extended beyond the diameter of the last whorl, and less axially deflected last whorl. This new species differs from H. bombax by having an angular penultimate whorl, more axially deflected last whorl, subcircular aperture, and broadly expanded lip. In comparison, H. bombax has a rounded penultimate whorl, less axially deflected last whorl, semi-ovate aperture, with thickened and slightly expanded lip. For further comparison, H. karenorum sp. nov. differs from H. burmanicus, H. blanfordi, and H. thebawi in having a more axially deflected last whorl, lower spire, penultimate whorl angular and strongly extended beyond the diameter of the last whorl, and without sinulus. The three latter species have an elevated spire, penultimate whorl rounded and slightly extended beyond the diameter of the last whorl, and less axially deflected last whorl.

Shell oblique-ovate, solid and translucent; whorls 6–7½; spire depressed convex and with distinct suture. Embryonic shell ~ 2½ whorls with smooth surface; following whorls growing regularly and last whorl intermediately expanded. Shell surface has moderately strong radial ridges that diminish below periphery of last whorl and around umbilicus. Penultimate whorl bluntly angular and extended beyond last whorl. Last whorl compressed to flattened, axially deflected from columellar axis. Aperture subcircular; peristome thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella. Umbilicus widely open and deep (Fig. 14C–E).

The specific name karenorum refers to the Karen people, the major ethnicity in Kayin State, Myanmar.

This species is known from two localities in the limestone karts of Kayin State, southern Myanmar.

Comparing populations from the two localities, shells of H. karenorum sp. nov. from the Taung Lay population (Fig. 14E) have a more elevated spire and weaker parietal lamella. However, the bluntly angular penultimate whorl and oblique ovate shells are identical to the type specimens, which we consider an intraspecific shell variation. However, these two localities are quite distant from each other, and on opposite sides of the Attaran River (Fig. 1). Thus further, genitalia information will help determine whether they are just geographical variations.

Carinartemis vesperus Siriboon & Panha, 2014 by original designation.

Shell obliquely heliciform and with conical spire. Penultimate whorl keeled and extended beyond the diameter of the last whorl. Last whorl rounded to shouldered and strongly axially deflected. Aperture semi-ovate to subcircular; apertural dentition with or without one or two parietal lamellae. Genitalia with thin to thick penial sheath that covers entire penis length; penial hooks and vaginal hooks may be present.

The genus is comprised of two endemic species occurring in limestone outcrops in western Thailand. A recent phylogenetic study revealed that the previously recognized Haploptychius petitii (Gould, 1844) and Indoartemon medius Siriboon & Panha, 2014 are clustered with members of the Carinartemis (see Siriboon et al. 2020) with strong support. Siriboon et al. (2020) suggested reassigning these two species into Carinartemis. Therefore, based on this phylogenetic result, the previously recognized H. petitii is relocated here under the genus Carinartemis.

Syntype MCZ 169290 (1 shell; Fig. 17A) from Burmah. Moulmein: NHMUK 1909.3.15.67 (2 shells, Fig. 17B) ex. Godwin-Austen collection. NHMUK 67.9.3.15 (1 shell) ex. Blanford collection.

Figure 17. 

A, B Carinartemis petitii A syntype MCZ 169290 from Tavoy, British Burmah and B specimen NHMUK 1909.3.15.67 from Moulmein C, D Carinartemis exacutus C specimen NHMUK 1888.12.4.771–773 from Moulmein with apertural dentition and D specimen CUMZ 13025 from Taung Wine Cave, Hpa-an, Kayin State with apertural dentition.

Carinartemis petitii can be distinguished from C. sankeyi (Benson, 1859) by having a fine transverse ridge on the upper periphery, penultimate whorl keeled and little extended beyond the diameter of last whorl, and a subcircular aperture. In addition, C. petitii differs from I. medius from Thailand by having a more axially deflected last whorl, and only one parietal lamella present, while I. medius has a less axially deflected last whorl, and with one additional small palatal lamella. Carinartemis petitii is superficially similar to H. blaisei but it has an elevated spire, keeled penultimate whorl, subcircular aperture, and thicker lip.

Shell oblique-heliciform, white, and translucent; whorls 6½–7; spire conical with distinct suture. Shell surface glossy with fine transverse ridges, nearly smooth with a few transverse ridges near peristome. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery keeled nearly the entire penultimate whorl; last whorl axially deflected. Aperture subcircular; peristome discontinuous, thickened, expanded, and reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Fig. 17A, B).

This species is known from the type locality in Myanmar (Gould 1844) and Kanchanaburi Province in Thailand (Siriboon et al. 2020).

No new specimens were collected in this survey. However, the syntype (Fig. 17A) and the museum specimens (Fig. 17B) show slightly different shell forms. Carinartemis petitii is similar in shell form to the genus Haplotychius in having one parietal lamella and a deflected last whorl. However, an initial molecular analysis placed this species within the Carinartemis clade (Siriboon et al. 2020). This species is clearly distinct from other recognized Carinartemis species by its oblique-heliciform shell, translucence and a high to low conical spire with a distinct suture. Moreover, the shell surface has fine transverse ridges that diminish below periphery, whorls regularly coiled, shell periphery is keeled; umbilicus open and deep. Aperture is semi-ovate, peristome thickened, expanded, reflected, and apertural dentition with one strong parietal lamella.

Moulmein: NHMUK 1874.9.3.15 (3 shells) ex. Godwin-Austen. NHMUK 1888.12.4.771–773 (3 shells; Fig. 17C). NHMUK 1906.2.2.198 (3 shells + 2 juveniles; Fig. 18A) ex. Blanford collection. NHMUK 1903.7.1.3999 (3 shells) ex. Godwin-Austen collection. Burma: NHMUK1950.12.9.170 (1 shell) ex. Laidlaw collection. Mergui: NHMUK ex. Cuming collection (2 shells). Sadhdan Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°44'23.4"N, 97°43'04.2"E): CUMZ 13020 (3 shells). Bayin Nyi Cave, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°58'10.1"N, 97°29'30.6"E): CUMZ 13021 (8 shells; Fig. 18B), CUMZ 13022 (15 specimens in ethanol). Lun Nga Mountain, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°44'53.2"N, 97°47'09.5"E): CUMZ 13023 (14 shells; Fig. 18C), CUMZ 13024 (50 specimens in ethanol). Taung Wine Cave, near Thiri Hpa-an Hotel, Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°50'31.1"N, 97°37'18.4"E): CUMZ 13025 (3 shells; Fig. 17D), CUMZ13026 (6 specimens in ethanol). Kaw Ka Taung Cave (Golden valley), Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°50'32.4"N, 97°37'10.9"E): CUMZ 13027 (1 shell).

Figure 18. 

Carinartemis exacutus A specimen NHMUK 1906.2.2.198 from Moulmein B specimen CUMZ 13021 from Bayin Nyi Cave, Hpa-an, Kayin State C specimen CUMZ 13023 from Lun Nga Mountain, Hpa-an, Kayin State with apertural dentition.

Carinartemis exacutus is superficially similar to C. sankeyi, C. vesperus Siriboon & Panha, 2014, and C. striatus Siriboon & Panha, 2014 from western Thailand, but it has a larger shell, convex spire, immediately expanded penultimate whorl, semi-ovate aperture, two parietal lamellae, very thickened penial sheath, vas deferens passes through penial sheath, curved portion of vas deferens with very thin connective tissue, and hooks located on irregular trapezoidal penial papillae separated by longitudinal folds. In comparison, C. sankeyi, C. vesperus, and C. striatus have an elevated spire, regularly expanded penultimate whorl, but C. sankeyi has fine transverse ridges on the entire shell, subquadrangular aperture, one parietal lamella, slender atrium, thin penial sheath, vas deferens does not pass through a penial sheath, curved portion of vas deferens is without connective tissue, proximal penial hook located on laterally-flattened penial papillae, and distal penial hooks located on laterally compressed penial papillae separated by reticulated folds. In contrast, C. vesperus has a subcircular aperture, lacks parietal lamellae, has a less axially deflected last whorl, vas deferens passes through the penial sheath, curved portion of vas deferens is without connective tissue, and penial papillae absent. Meanwhile, C. striatus has strong transverse ridges over the entire shell, a semi-ovate aperture, one parietal lamella, vas deferens is attached to the distal end of the penial sheath with very thin connective tissue, and hooks are located on papillae without connected longitudinal folds.

Shell oblique-heliciform, white, and translucent; whorls 6–6½; spire convex with distinct suture. Shell surface glossy with fine transverse ridges, nearly smooth with few transverse ridges near peristome; varices present. Embryonic shell ~ 2½ whorls with smooth surface; following whorls intermediately coiled. Shell periphery wide and sharply keeled along nearly the entire penultimate whorl; last whorl axially deflected. Aperture semi-ovate; peristome discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella and sometimes with a second parietal lamella adjoined at a right angle. Umbilicus open and deep (Figs 17C, D, 18).

Genital organs. Atrium (at) short. Penis (p) a very thin, and long tube. Penial sheath (ps) muscularly enlarged, very thickened and extending entire length of penis; penial sheath retractor muscle (psr) thin, originating near genital orifice, attached to atrium with short and thin connective tissue, and inserting distally on penial sheath (Fig. 21A). Vas deferens (vd) passes through a short portion of penial sheath, then extends to curved portion at ~ 1/11 of the penial sheath length before entering penis distally. Curved portion of vas deferens with very thin connective tissue originating at penial sheath (Fig. 21B). Penial retractor muscle (pr) thin, very long, inserting at penis and vas deferens junction.

Internal wall of atrium generally smooth with sparse atrial pores (Fig. 22A). Penial wall with scattered pale brownish penial hooks, ~ 20 hooks/200 μm²; hooks located on laterally flattened penial papillae and separated by longitudinal folds (Fig. 22B–D). Penial hooks small (<0.02 mm in length), expanded at base, tips pointed and curved towards genital orifice (Fig. 22E, F).

Vagina (v) very short and ~ 1/12 of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Proximal free oviduct (fo) enlarged then tapering to smaller diameter distally. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club shaped. Hermaphroditic duct (hd) bearing long seminal vesicle (sv) ~ 1/2 the length from talon to branching point of seminal vesicle (Fig. 21A).

Vaginal wall with longitudinal oblique vaginal folds, folds with nearly smooth surface and vaginal hook absent (Fig. 22G).

Radula. Each row consists of 41–45 teeth with formula (22–20)–1–(20–22). Central tooth is very small with pointed cusp. Lateral and marginal teeth undifferentiated, lanceolate, unicuspid, and lanceolate. Latero-marginal teeth gradually reduced in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24D).

This species was collected from five limestone hills in Kayin State, southern Myanmar, in this survey.

This species appears at a high abundance among the limestone karsts in Hpa-an, Kayin State. All the specimens examined from the populations from Lun Nga Mountain and Bayin Nyi Cave have a very small to indistinct upper parietal lamella, and some specimens from Bayin Nyi Cave have strong transverse ridges on almost the entire whorl. Moreover, the Lun Nga Mountain population have a last whorl that is more extended anteriorly and an elongated semi-ovate aperture (Fig. 18C). However, the genitalia in all localities show no difference from this locality; thus, we consider them as intraspecific variations within C. exacutus. Some specimens from Bayin Nyi Cave have strong transverse ridges on almost the entire whorl.

Although the type locality was listed as ‘Burma’ [Myanmar], all the known records and specimens examined in this study were collected from Kayin State. Therefore, the precise type locality of this species is probably southwestern Myanmar in Mon State and Kayin State.

Syntype UMZC I.102740 (6 shells; Fig. 19A) from Moulmein. Moulmein: NHMUK 1954.6.3.556 (1 shell) ex. Hawkins collection. NHMUK 1906.2.2.341 (4 shells; Fig. 19C) ex. Blanford collection. NHMUK 1872.9.3.15 (5 shells) ex. Godwin-Austen collection. NHMUK 1903.7.1.4001 (1 shell; Fig. 20A) ex. Godwin-Austen collection. NHMUK Acc. No. 1733 ex. Oldham collection (2 shells). NHMUK 1888.12.4.792–794 (3 shells; Fig. 19B). NHMUK 1871.9.23.61 (1 shell; Fig. 19D). Paboung Toung, Burma: NHMUK 1891.3.17.577–578 (2 shells) ex. Hungerford collection. Mergui: NHMUK 20210051 (1 shell; Fig. 19E) ex. Cuming collection. Kwengan Hill: NHMUK 1888.12.4.781–783 (3 shells; Fig. 20B) ex. Blanford collection. Saddan Cave situated on same karsts ~ 600 m south of Kayon Cave, Mawlamyine Township, Mawlamyine District, Mon State, Myanmar (16°31'42.8"N, 97°43'2.1"E): CUMZ 13028 (7 shells). Kayon Cave [previously known as Farm Caves] ~ 10 km from Mawlamyine Township, Mawlamyine District, Mon State, Myanmar (16°32'0.5"N, 97°42'53.5"E: CUMZ 13029 (13 shells; Fig. 20D), CUMZ 13030 (5 specimens in ethanol). Dhammatat Cave, Mawlamyine Township, Mon State, Myanmar (16°30'23.0"N, 97°48'36.3"E): CUMZ 13031 (12 shells; Fig. 20C).

Figure 19. 

Carinartemis sankeyi A syntype UMZC I.102740 from Moulmein B specimen NHMUK 1888.12.4.792–794 from Moulmein C specimen NHMUK 1906.2.2.341 from Moulmein with apertural dentition D specimen NHMUK 1871.9.23.61 from Moulmein E specimen NHMUK ex. Cuming collection from Mergui.

Figure 20. 

Carinartemis sankeyi A specimen NHMUK 1903.7.1.4001 from Moulmein B specimen NHMUK 1888.12.4.781–783 from Kwengan Hill C specimen CUMZ 13031 from Dhammatat Cave, Mawlamyine, Mon State with apertural dentition D specimen CUMZ 13029 from Kayon Cave, Mawlamyine, Mon State with apertural dentition.

Carinartemis sankeyi is superficially similar to C. vesperus and C. striatus in having a subquadrangular aperture, and less expanded and continuous peristome, slender atrium, vas deferens does not pass through a penial sheath, proximal penial hooks located on laterally flattened penial papillae, and distal penial hooks located on laterally compressed penial papillae separated by reticulated folds. In contrast, the shell of C. vesperus has fine transverse ridges (nearly smooth) with few transverse ridges near peristome, varices absent, periphery more extended beyond the diameter of last whorl, lacking parietal lamella, and penial papillae absent. Meanwhile, C. striatus has vas deferens attached to the distal end of penial sheath with very thin connective tissue, and hooks located on papillae without connected longitudinal folds.

Shell oblique-heliciform, white, translucent; whorls 6–7; spire conical with distinct suture. Shell surface glossy with fine transverse ridge across the entire shell; varices present. Embryonic shell ~ 2½ whorls with smooth surface; following whorls regularly coiled. Shell periphery wide and sharply keeled around nearly the entire penultimate whorl; last whorl axially deflected. Aperture subquadrangular; peristome continuous, thickened, expanded, and reflected. Apertural dentition with one strong parietal lamella. Umbilicus open and deep (Figs 19, 20).

Genital organs. Atrium (at) short, thin and slender. Penis (p) very thin and long. Penial sheath (ps) thin and extending nearly entire length of penis; penial sheath retractor muscle (psr) thin, originating near genital orifice and attached to atrium with short and thin connective tissue, and inserting distally on penial sheath (Fig. 21C). Vas deferens (vd) runs downwards to curved portion, ~ 1/3 of the penial sheath length, without insertion before entering penis distally (Fig. 21D). Penial retractor muscle (pr) thin, very long, inserting at penis and vas deferens junction.

Figure 21. 

Genital anatomy of A, B Carinartemis exacutus, specimen CUMZ 13021 A reproductive system and B insertion of vas deferens into penial sheath C, D Carinartemis sankeyi, specimen CUMZ 13029 C reproductive system and D insertion of vas deferens into penial sheath.

Figure 22. 

Internal sculpture of genitalia of Carinartemis exacutus, specimen CUMZ 13021 A atrium surface B overview of internal penial wall C arrangement of penial hooks on proximal part of penis D lateral view of penial hooks E arrangement of penial hooks on middle part of penis F lateral view penial hooks G arrangement of longitudinal oblique vaginal folds.

Internal wall of atrium generally smooth with sparse atrial pores (Fig. 23A). Proximal penial wall covered with scattered and pale brownish penial hooks, ~ 12 hooks/200 μm². Proximal penial hooks located on laterally flattened penial papillae; hooks small and short (< 0.03 mm in length), slightly expanded at base, tips obtuse and curved towards genital orifice (Fig. 23B, C). Middle and distal penial walls densely covered with pale brownish hooks, ~ 20 hooks/200 μm². Middle and distal hooks located on laterally compressed penial papillae separated by reticulated folds; hooks small, short (<0.01 mm in length), slightly expanded at base, and tips pointed (Fig. 23D–G).

Figure 23. 

Internal sculpture of genitalia of Carinartemis sankeyi, specimen CUMZ 13029 A atrium surface B arrangement of penial hooks on proximal part of penis C lateral view of exposed proximal penial hooks D penial hooks on middle part of penis E arrangement of penial hooks on distal part of penis F uncovered distal penial hooks with pointed tip G distal penial hooks embedded in penial papillae H vaginal surface with vaginal pores.

Vagina (v) short, stout and ~ 1/5 of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Proximal free oviduct (fo) enlarged then tapering to smaller diameter in middle section, and slightly enlarged distally. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club shaped. Hermaphroditic duct (hd) bearing long seminal vesicle (sv) ca. the same length as from talon to branching point of seminal vesicle (Fig. 21C).

Vaginal wall generally smooth with vaginal pores, and vaginal hook absent (Fig. 23H).

This species occurs from three localities in Mon State, southern Myanmar and is likely to be endemic to this area.

Each row consists of 43–49 teeth with formula (21–24)–1–(21–24). Central tooth small with pointed cusp. Lateral and marginal teeth undifferentiated, unicuspid and lanceolate. Latero-marginal teeth gradually reduced in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24D).

Figure 24. 

Radula of specimens A Discartemon tonywhitteni, paratype CUMZ 13001 B Discartemon paurodeviatus sp. nov., paratype CUMZ 13003 C Haploptychius heliakosus sp. nov., paratype CUMZ 13014 D Carinartemis exacutus, specimen CUMZ 13021 E, F Carinartemis sankeyi, specimen CUMZ 13029 E overview of radula and F high magnification of central teeth.

Benson (1859a) introduced C. sankeyi based on a single specimen from ‘Moulmein’. Later, Stoliczka (1871) provided some diagnostic characters with a description of the soft body color and suggested that the Farm-Cave is possibly the correct type locality. This historical locality name refers to a group of caves located on a karst ridge, namely Kayon Hill, situated on the west bank of the Attaran River. At the same time, Stoliczka (1871) proposed Streptaxis hanleyanus based on a single specimen with a small and depressed shell, wide umbilicus, and almost rectangular aperture. However, this holotype specimen was collected from the same geographical area as C. sankeyi. Therefore, we consider this nominal species as a smaller shell form and so treat it as a junior synonym with C. sankeyi.

The original spelling of this nominal species was sankeyi, which was intentionally modified to sankeyanus by Stoliczka (1871) without a clear reason. Therefore, this unjustified emendation name was made available with its authorship and date and became a junior objective synonym (ICZN 1999: Arts 32.3, 33.2.3, 50.5).

Recently, the population collected from Dhammatat Cave showed a more rectangular aperture, slightly compact penultimate whorl, and larger parietal lamella (Fig. 20C), but this species could only be examined from the empty shells. Therefore, we have to conclude that these differences are an intraspecific variation until more specimens are available, or at least the genitalia.