Helix (Plectopylis) Leiophis Benson, 1860 (Figure 2) by original designation.

Shell sinistral or dextral, flat, widely umbilicated; in most cases protoconch seemingly “smooth” to the naked eye, but not glossy, rather matt; under the microscope usually tubercles of various size are visible (Figure 2B); sometimes the tuberculated protoconch is irregularly wrinkled; flat periostracal filaments are visible on the body whorl or on the dorsal surface in only a few species; aperture always with a fold; parietal wall with one vertical lamella and usually one or two long horizontal plicae (main plica and lower plica) reaching the callus; palatal plicae horizontal, sometimes divided in the middle, in some species with several additional denticles posteriorly, in some species similar to that of Plectopylis (three horizontal plicae above and one below the vertical plate formed by the accretion of two plicae).

Only one Chersaecia species is known anatomically (Ch. simplex in the original description: Solem 1966). Penis internally with approximately eight longitudinal rows, those situated next to the vas deferens are distinctly larger; vas deferens becomes a part of the penis wall at the penioviducal angle; no epiphallic differentiation observed; retractor muscle inserts on the dorsal surface of the penis and attaches to the diaphragm; diverticulum absent, gametolytic sac long and thickened.

Chersaecia differs from Endothyrella, Gudeodiscus Páll-Gergely, 2013, Halongella Páll-Gergely, 2013, Sicradiscus Páll-Gergely, 2013 and Sinicola by the usually tuberculated (not regularly ribbed) protoconch. The presence of long parietal plicae (main and lower) distinguishes most Chersaecia species from most Endothyrella, Gudeodiscus, Halongella, Sicradiscus and Sinicola species. The delimitation of Chersaecia from Plectopylis and Endoplon needs further investigation. Among all plectopylids examined to date Chersaecia simplex is the only species found to lack an epiphallus. The anatomy of more Chersaecia species should be studied to check the taxonomic value of the lack of the epiphallus.

austeni, brachydiscus, degerbolae, dextrorsa, kengtungensis, leiophis (pseudophis is probably a synonym, see Gude 1908a), muspratti, nagaensis, perarcta, perrierae, refuga, shanensis, shiroiensis, simplex.

The genus is known to inhabit northeastern India, eastern and southern Myanmar (Burma) and northern Thailand.

Helix plectostoma Benson, 1836, by original designation.

Shell sinistral or dextral; protoconch usually finely, regularly ribbed (see also discussion and Figures 6A–F); periostracal folds usually present on the body whorl; they are arranged in 3–7 lines; folds hair-like in most species, resulting from the rolling of flat folds; folds flat (not rolled) in some species only (see Figures 8D, 20A–F); dorsal sculpture strong, usually reticulated (both radial and spiral lines present, see Figure 8A); umbilicus wide to narrow; body whorl rounded in some species but rather bluntly shouldered (keeled) in others; apertural fold always absent; main plica usually absent (present in a few species only); low plica (if present) runs close to and parallel with the lower suture, it is usually very short (present only under the lamella), but in some species it reaches the callus; parietal wall with a single lamella with denticles posteriorly (probably homologous with the posterior lamella); two lamellae were reported in one species (E. aborensis) only; palatal plicae complicated in most species with many small denticles at their posterior ends; in many species they are at least party divided in the middle.

Genitalia (see Figures 18, 21, 22B–F, 25, 26): The left ommatophoral retractor passes between penis and vagina (in sinistral species). Penis internally with hollows (small pocket-like structures) having calcareous granules inside; penial papilla absent; epiphallus may be longer than penis and enters penis laterally; epiphallus with longitudinal folds internally; small penial caecum usually present at the penis-epiphallus boundary; retractor muscle inserts on the caecum and attaches to the diaphragm; diverticulum (if present) and gametolytic sac are of the same size.

Radula (see Figures 19A–F): Central tooth larger than the ectocones of the first laterals; marginals tricuspid (= ectocones are divided) or even quadricuspid (both the endocones and ectocones are divided); the incision between the ectocones and endocones usually deep (E. fultoni has rhomboid marginals which are unique in the whole family).

All known species of the genera Sinicola, Gudeodiscus, Halongella and Sicradiscus are dextral. Regardless of the coiling direction, most Endothyrella species differ from Sinicola by the presence of usually hair-like periostracal folds standing in multiple lines. Deciduous periostracal folds in Sinicola are present only along the keel and the folds are always flat. Most Sinicola species (especially the large species) have a sharp keel, whereas Endothyrella species usually have a rounded or slightly keeled, shouldered body whorl. The palatal plicae of Sinicola are usually simple, horizontal, straight and parallel, but in Endothyrella they are often oblique to vertical, divided and ornamented with minute denticles at their posterior ends. In Sinicola the posterior lamella is present on the parietal wall, with two horizontal plicae anteriorly above and below, whereas in most Endothyrella species (probably except for E. aborensis) the anterior lamella is present and the posterior is missing or reduced to one or two short vertical plicae.

Some Gudeodiscus and Halongella species possess low, radial periostracal folds (e.g. Páll-Gergely et al. 2015, fig. 10e–f), similar to those of E. nepalica sp. n. (see there). The radial folds have serrated edges in Gudeodiscus phlyarius (Mabille, 1887). The tiny tips of the serrated folds seem to occur in a spiralling pattern (see Páll-Gergely and Hunyadi 2013, fig. 113 and Páll-Gergely et al. 2015, fig. 10c–d). All of these periostracal features of Gudeodiscus and Halongella are, however, easily distinguishable from the long, hair-like folds of the genus Endothyrella.

Some Gudeodiscus species possess a fold in the aperture, which is always missing in Endothyrella. The palatal plicae in Gudeodiscus are usually depressed Z- or L-shaped and posterior small denticles are very rare (except for one denticle above the posterior end of the last plica), whereas the palatal plicae of Endothyrella are frequently divided in the middle and posterior small denticles are usually present. In Endothyrella the anterior lamella is present, and often the upper horizontal plica is missing, whereas in Gudeodiscus both lamellae, or only the posterior one, are visible and the upper horizontal plica (above the lamella) is almost always present. Additionally, Gudeodiscus species have a rounded body whorl, while in many Endothyrella species the body whorl is angled or shouldered. Our limited knowledge on the anatomy of Endothyrella species shows that the entire inner penial wall of Endothyrella is covered by pits, whereas in Gudeodiscus these pocket-like structures are restricted to the a certain (usually apical) portion of the penis.

Sicradiscus is similar to Endothyrella in possessing a weak or reduced posterior lamella. Long periostracal folds standing in more than one row have also been found in one Sicradiscus species, namely in juveniles of Sicradiscus transitus Páll-Gergely, 2013. This species, however, has hairs standing in two spiral lines on the body whorl, whereas in Endothyrella the hairs are arranged in 3–7 spiral lines. This trait seems to be absent in adult S. transitus shells and all other species of Sicradiscus, but is common in fully grown Endothyrella shells (i.e. most species possess them). The two genera (i.e. Endothyrella and Sicradiscus) differ in the short, straight palatal plicae, which are usually connected in Sicradiscus vs. longer, more complex palatal plicae sometimes having additional denticles in Endothyrella. In both genera divided plicae may occur, but in the case of Sicradiscus the posterior fourth and fifth plicae seem to be always connected, whereas in Endothyrella all plicae are free. Moreover, western Sicradiscus species (feheri Páll-Gergely, 2013, invius [Heude, 1885], mansuyi [Gude, 1908b], securus [Heude, 1885] and transitus) differ from Endothyrella by the presence of a strong apertural fold.

Plectopylis and Endoplon species have a granulated or smooth protoconch, whereas it is usually finely ribbed in Endothyrella. Moreover, Plectopylis and Endoplon usually have a strong apertural fold which is often connected to a long main plica. In contrast, although some Endothyrella species have a main plica, they all lack an apertural fold. See also under Chersaecia and Table 3.

aborensis, affinis, angulata sp. n., babbagei, bedfordi, blanda, brahma, dolakhaensis sp. n., fultoni, inexpectata sp. n., macromphalus (syn.: gregorsoni), minor, miriensis, nepalica sp. n., oakesi, oglei, pinacis, plectostoma, robustistriata sp. n., serica (syn: munipurensis), sowerbyi, tricarinata, williamsoni. See also Tables 4 and 5.

The distribution of this genus is restricted to Nepal, northeastern India and the province Sichuan in China. One species (E. plectostoma) was reported from Myanmar (Figure 3).

Peak Luyor, Abor Hills, 7,200 ft, leg. C.F.G. Oakes R.E., NHMUK 1903.7.1.3529. (holotype, Figures 4A, 6C).

Shell small, dextral, slightly concave above; widely umbilicated; hairs arranged in three spiral lines on the body whorl; callus strong, palatal plicae short, simple, parietal wall with a single curved lamella.

(in mm): D: 14.4, H: 6.3 (n = 1).

For differences with E. oglei, and E. serica and E. inexpectata sp. n., see there. See also Table 5.

Only known from the type locality (Figure 7).

China, Sichuan Sheng (四川省), Panzhihua Shi (攀枝花市), Yanbian Xian (盐边县), Qinghe Xiang (箐河乡), Qinghepubu (箐河瀑布), Xianrendong (仙人洞), 1410 m, 27°03.834'N, 101°23.611'E, leg. Hosoda, T., Ohara, K., Okubo, K., Otani, J. U., 12.09.2013, NHMUK 20140023 (holotype, Figures 4B, 6F, 8D, 9A–B), JUO/1 (paratype), TH/1 (paratype = juvenile shell); China, Sichuan Sheng (四川省), Liangshan Yizu Zizhizhou (凉山彝族自治州), Yanyuan Xian (盐源县), Bainiao Zhen (白鳥鎮), Kedengrongdong (柯登溶洞) (cave), 2620 m, 27°43.103'N, 101°31.021'E, leg. Hosoda, T., Ohara, K., Okubo, K., Otani, J. U., 13.09.2013, JUO/1 juvenile shell (not paratype); Sichuan Sheng (四川省), Liangshan Zhou (凉山州), Yanyuan Xian (盐源县), Baiwu Zhen (白乌镇), eastern edge of Kedeng Cun (柯登村), 2640 m, 27°43.897'N, 101°31.208'E, leg. Hunyadi, A., Szekeres, M., 11.06.2015., HA/1 paratype.

Shell very small, dextral, almost flat, relatively widely umbilicated with elevated callus; hairs standing in three lines on the body whorl; parietal wall with a single, curved lamella; palatal wall with six short plicae.

Shell dextral, with almost flat, very slightly domed dorsal side (protoconch slightly elevates from the dorsal surface); brownish or slightly reddish in colour; protoconch consists of 1.5–1.75 whorls, first whorls rather smooth, last 0.25–0.5 whorl regularly ribbed (Figure 6F); teleoconch with irregular, rough growth lines and spiral structure; sculpture stronger on the dorsal surface but still well-visible on the ventral surface; deciduous, slim and flat folds standing in three lines on the body whorl (Figure 8D); whorls 4.75, very much bulging, separated by deep suture; umbilicus moderately wide and deep; apertural lip whitish, thickened and slightly reflexed; callus strong, elevated, sharp and slightly S-shaped; with canals at both ends; no fold in the aperture.

One specimen (the holotype) was opened. The armature is situated very close to the aperture, palatal plicae visible from oblique view through the aperture. Parietal wall with a single curved lamella without additional denticles; arms of the lamella pointing posteriorly; palatal wall with six very short plicae becoming narrower posteriorly; the last one with an additional denticle posteriorly (Figures 9A–B).

(in mm): D: 6.6–6.7, H: 3.0–3.1 (n = 2, from different localities).

Endothyrella babbagei is much larger than E. inexpectata sp. n., and it has flatter whorls and has a weaker callus than the new species. Sinicola species of the same size have a keeled or shouldered body whorl and have two parallel parietal plicae anterior to or above the lamella (one near the upper, the other near the lower suture). Sicradiscus invius also occurs in Sichuan, but it is smooth (glossy) and has a strong apertural fold. See also under Endothyrella oglei and E. serica and Table 5.

The name inexpectata (meaning unexpected in Latin) refers to the surprizing new, especially dextral Endothyrella species in China.

Sichuan Sheng (四川省), Panzhihuashi (攀枝花市), Yanbian Xian (盐边县), Qinghe Xiang (箐河乡), Qinghepubu (箐河瀑布), Xianrendong (仙人洞), 1410 m, 27°03.834'N, 101°23.611'E.

Endothyrella inexpectata sp. n. is known from two localities in western Sichuan province, China (Figure 7).

Sadia, E. Assam, leg. Ogle, NHMUK 1903.7.1.740. (4 syntypes, Figure 5A, 6A).

Shell middle sized, dextral, yellowish-reddish striped with moderately wide umbilicus and somewhat domed dorsal surface; callus strong, palatal plicae divided at their middle and the posterior fragments are connected by a ridge; parietal wall with a single curved lamella with posteriorly elongated upper and lower ends. Probably at least the upper elongation is homologous with the posterior denticle of other Endothyrella species.

(in mm): D: 16.8–16.9, H: 7.7–8.1 (n = 2, type series).

Endothyrella babbagei and E. inexpectata sp. n. differ from the E. oglei by the flat dorsal surface of the shell and the presence of hairs arranged in three rows on the body whorl. See also under E. serica and Table 5.

The information published by Gude (1914b) (major diameter 27, minor diameter 25 mm) is wrong; it probably refers to “Chersaecia” andersoni.

The species is known from the type locality only (Figure 10).

Khunho, H.S. Naga Hills, leg. Godwin-Austen, NHMUK 1903.7.1.741 (8 syntypes of serica, Figure 5B); Hengdan P., Naga Hills, leg. Godwin-Austen, NHMUK1903.7.1.744 (6 syntypes of serica, Figure 5C); Munipur Hills, head of the Ihang valley, Munipur, leg. Godwin-Austen, NHMUK 1903.7.1.742. (6 syntypes of munipurensis, Figure 5D).

Naga Hills, coll. Godwin-Austen, NHMUK 1903.7.1.743/4 (under the name munipurensis); Japvo Peak, Nr. Kohima, Naga Hills, NHMUK 20150128/8; Lhota Naga, coll. Godwin-Austen, NHMUK 1903.7.1.745/6; no locality, leg. Maxwell, coll. Godwin-Austen, NHMUK 20150129/5; India, Hengdan Peak, NHMUK 1891.3.17.356–357/2; India, NHMUK 1874.4.26.2/2; Khasi Hills, coll. W. Blanford, NHMUK 1906.2.2.360/2.

Shell very small to small, dextral, yellowish-reddish striped with moderately wide umbilicus and depressed conical dorsal surface; callus strong, palatal plicae more or less straight, simple or have dichotomously divided posterior ends; parietal wall with a single curved lamella with denticles near the upper and lower ends posteriorly, which occasionally fuse with the lamella.

(in mm): D: 9.7–9.9, H: 4.4–4.8 (n = 3, NHMUK 1903.7.1.744); D: 9.9–13, H: 4.9–5.5 (n = 4, NHMUK 1903.7.1.741); D: 10.9–11.7, H: 5.1–5.7 (n = 3, NHMUK 1903.7.1.742).

Endothyrella babbagei and E. inexpectata sp. n. differ from E. serica by the flat dorsal surface of the shell and the presence of three rows of hairs on the body whorl. Endothyrella oglei differs from the also dextral E. serica by the much larger size, the absence of the groove on the protoconch, which runs parallel with the suture in E. serica, and the morphology of the lamella which has only posteriorly elongated ends. See also Table 5.

The species is recorded from the Naga Hills (see also remarks). “Plectopylis munipurensis” was described from “end of the Ihang valley” (Figure 11).

Godwin-Austen (1875) described Helix (Plectopylis) serica and Helix (Plectopylis) munipurensis in the same publication. He did not mention the differences between the two species. According to the illustrations and the identification key in the original description, the upper end of the lamella in munipurensis is more elongated anteriorly than that of H. serica. Two shells of E. serica were opened from the Hengdan sample, and both had an anteriorly elongated plica. In this respect, and also in shell shape, these shells were more similar to E. munipurensis specimens. In the Khunho sample four shells were opened, three having no or very slight upper elongation, but one had an as long plica as in typical munipurensis shells. Examining the type specimens of the two species we have not found significant differences. The width of the umbilicus and the height of the spire showed some variability. Therefore we synonymize munipurensis with serica. We choose Helix (Plectopylis) serica to be the valid specific name.

In the original description Godwin-Austen (1875) reported the species from the “peak of Henozdan” and from the “Kopamedza ridge”. The second sample is probably identical with the one from Khunho in the type collection of the NHM.

Gude (1897h) mentions that according to Godwin-Austen, the correct names for “Henozdan” and “Kopameda” in Gude (1897a) are “Hengdan” and “Kopamedza”, respectively. According to the same erratum, Godwin-Austen also mentioned that the locality of Ponsonby’s shell (Sylhet) is probably incorrect, because Plectopylis serica is a very local species, inhabiting altitudes higher than 5000 feet.

According to the original description, two shells, an adult and a juvenile were collected and finally deposited in the Indian Museum (inventory numbers: 5998 and 6135). Specimen reference collections in the Indian Museum were transferred to the ZSI following foundation of the ZSI in 1916. The ZSI supplied us with two photos of an adult shell under the name of Plectopylis aborensis, which they considered as one of the type specimens. These photos, however, clearly showed a different specimen than the one figured in Gude (1915). No other information could be obtained from the ZSI.

Shell small, sinistral, almost flat, widely umbilicated; callus strong; palatal plicae Z or L-shaped; there are two parietal lamellae, a short upper plica which is in contact with the posterior lamella, and a long lower plica which reaches the peristome.

(in mm): D: 14, H: 6.5 (according to the original description).

The species was not examined by us, but according to the original description the species differs from all congeners by the short and uniquely shaped palatal plicae, which are depressed Z-shaped, or the lower branch of the “Z” is elongated. See also Table 5.

Known from the type locality only (approximately 28°10'N, 95°13'E) (Figure 10).

So far, this is the only Endothyrella species with two well-developed lamellae. The parietal lamellae show a very unusual arrangement which has not been observed in any other species of Plectopylidae. The two parietal plicae can be the result of teratological duplication which has been reported for some species (Gude 1908b: 347).

India, Khasia Hills, ex Fulton, NHMUK 1922.8.29.36 (syntype, Figure 13G); Khasia Hills, NHMUK 1901.4.25.41–43 (3 syntypes).

India, Khasi Hills, NHMUK 1892.9.22.1–4 (4 specimens); India, NHMUK 1916.3.15.1–2/2 (“showing immature armature”); Khasi Hills, Assam, coll. Salisbury ex coll. Beddome, NHMUK 20150130/3; Khasi Hills, NHMUK 20150131/3; Cherra, leg. Godwin-Austen, NHMUK 20150132/1 juvenile shell; N-Vorderindien, Khasi-Berge, coll. C. R. Boettger 1911, SMF 118096/1 (labelled as “cotype”); Cherrapoonjee, coll. Jetschin ex coll. Gude 1900, SMF 118095/2; India, Khasi Hills, NHMW 34233/2; Khasi Hills, coll. Möllendorff, SMF 150107/3; Khasi-Berge, coll. Möllendorff, ex coll. Gude, SMF 9279/4; Khasi Hills, coll. Bosch ex coll. Rolle, SMF 172074/2; N. O(?) Indien, coll. Steenberg, ZMUC-GAS-1811/1; no locality, coll. Jousseaume, MNHN 2012-27051/2; no locality, coll. Jousseaume, MNHN 2012-27048/29 (strongly shouldered, relatively small shells together with typical ones).

Shell small, sinistral, yellowish, with narrow umbilicus, conical dorsal surface and shouldered body whorl; hairs are arranged in four rows on the body whorl; callus strong, middle palatal plicae usually divided in the middle; the posterior fragments are oblique, the anterior ones are rather straight; parietal wall with a single, slightly curved lamella with short denticles posteriorly, one above and one below, and a horizontal lower plica which may be divided in the middle.

(in mm): D: 9.7–10.9, H: 5.4–5.7 (n = 4, SMF 9279); D: 8.5–10.6, H: 5.1–5.6 (n = 3, MNHN 2012-27048).

See under E. plectostoma, E. sowerbyi and E. tricarinata and Table 5.

The species is recorded from the Khasi Hills only (Figure 11).

Nepal, Taubas, Bhainse, Makwanpur District, 27°492521'N, 85°04839'E., leg. Budha, P., 30.03.2012., holotype (CDZMTU018, Figure 14B); 3 paratypes and 2 juvenile shells (not paratypes) (CDZMTU019).

Shell small, sinisttral, with flat dorsal surface and shouldered (keeled) body whorl; hairs are arranged in four rows; parietal lamella simple with a short free horizontal plica below it, and two denticles posterior to the lamella which are in contact with the lamella; middle palatal plicae divided.

Shell sinistral, semi-transparent; protoconch elevated from the flat dorsal surface; colour brownish or greyish; protoconch conspicuously large, consists of 2.5, 2.75 whorls, very finely, regularly ribbed; teleoconch with clearly visible reticulated sculpture dominated by radial growth lines; sculpture somewhat weaker on the ventral surface; very slender, long periostracal folds (hairs) standing in four spiral lines along the body whorl; two closely adjacent rows running with the keel above, one row on the ventral side around the umbilicus, and one row approximately in the middle line of the body whorl; whorls 6.25 (holotype) moderately bulging, separated by relatively deep suture; umbilicus wide and deep; peristome thin, slightly reflexed; callus moderate; no fold in the aperture.

One specimen was opened. Palatal wall with a single, straight lamella, with two short denticles on the posterior side of the lamella, both are in contact with the lamella; a short, free horizontal plica is visible under the lamella; palatal wall with six plicae, first straight, last slightly curved, the middle plicae are divided in the middle, the fragments are horizontal, oblique or Z-shaped (Figure 9I–J).

(in mm): D: 8.5, H: 3.5 (holotype); D: 5.5, H: 2.5, Wh: 5 (paratype; subadult specimen).

See under Endothyrella dolakhaensis sp. n., E. minor, E. nepalica sp. n., E. pinacis and Table 5.

The Latin angulatus (cornered, angular) refers to the shouldered/angulated body whorl of the new species.

Nepal, Taubas, Bhainse, Makwanpur District, 27°492521'N, 85°04839'E.

Endothyrella angulata sp. n. is known only from the type locality (Figure 15).

Tsanspu Valley Abor Hills, 2800 ft, leg. C.F.G. Oakes R.E., NHMUK 1903.7.1.3584. (2 syntypes, Figure 16C).

Shell very small, sinistral, brownish, with moderately wide umbilicus, almost flat dorsal surface (only the apex is elevated slightly), and rounded body whorl; callus strong, palatal plicae long, more or less straight horizontal, with dichotomously divided posterior ends and many small denticles at their posterior ends; lamella single, curved, in contact with a lower plica, which runs until the peristome.

(in mm): D: 9.1, H: 4.9 (n = 1, type series).

Endothyrella bedfordi has a single curved parietal lamella with a long lower plica (which reaches the peristome) attached to it, and at the posterior ends of palatal plicae there are several small denticles. These features distinguish E. bedfordi from all congeners. See also Table 5.

The species is known from the type locality only (approximately 28°44'N, 94°56'E) (Figure 10).

Naga Hills, NHMUK 1922.8.29.41., coll. Godwin-Austen (holotype, Figure 17B).

Richila Peak, Sikkim, India, coll. Ottó, L., MMGY 66425/2; Darjeeling, India, West Bengal, Darjeeling, North Point 900–1400 m asl., under stones in forest clearings, coll. Topál, 1967. HNHM 98849/2; Damsang, coll. Godwin-Austen, NHMUK 20150133/26; Rissetchu, Sikkim, coll. Godwin-Austen, NHMUK 20150135/8; Rissetchu & Richila Peak, W. Bhutan, coll. Godwin-Austen, NHMUK 20150136/33 (several of these are juvenile shells); Sikhim, Nampok, coll. Godwin-Austen, NHMUK 20150137/28; Richila Peak, Sikkim, coll. Godwin-Austen, NHMUK 20150138/102; Risset-Chu, Sikkim, NHMUK 20150139/309; Sikhim, NHMUK 20150140/8 (there is a label with the number “749”); Sikhim, coll. Beddome ex coll. Godwin-Austen, NHMUK 1912.4.16.318/1 (large variety); Sikhim, Rinkpo valley, NHMUK 1906.1.1.752/1; Sikkim, Rechila Peak, coll. W. Robert, NHMUK 1903.7.1.28/1; Sikhim, NHMUK 20150141/8; Sikkim, Rarhichu, coll. Godwin-Austen, NHMUK 20120110/1 (labelled as hanleyi?); Sikhim, Rarhichu, NHMUK 20150143/35 (mixed sample with E. minor); Darjiling, NHMUK 1906.2.2.142/5 (mixed sample with E. plectostoma); Rarhichu, NHMUK 20150134/49; Khasi Hills, leg. Stoliczka, 1880, NHMW 109255/3 (mixed sample with E. plectostoma: NHMW 92593 and E. sowerbyi: NHMW 109254).

Shell tiny to very small, sinistral, with narrow umbilicus, conical dorsal surface and 7 rows of hairs; callus weak but present; palatal plicae divided, posterior fractions denticle-like; anterior fractions horizontal, straight; lamella straight or very slightly S-shaped, with posterior denticles above and below, and with a lower and an upper plica close to the sutures; lower plica sometimes short, sometimes very long, and reaches the peristome.

(in mm): D: 4.9–5.7, H: 2.8–3.3 (n = 3, NHMUK 20150134).

See under E. macromphalus, E. minor, E. robustistriata sp. n. and E. williamsoni and Table 5.

(Figure 18): Two specimens were anatomically examined. Collection data: Silchar Cachar, F. Ede, coll. Godwin-Austen, NHMUK 1903.7.1.502. Both specimens had several embryos developing in the uterus.

The left ommatophoral retractor passes between penis and vagina. Atrium short, penis long, rather cylindrical, but slowly tapers towards the proximal end; opening the penis was very difficult, not only because of its size, but also due to the age of the specimen; the internal morphology could hardly be seen, although parallel folds forming “pockets” were visible; a little thickening was found near the posterior end of the penis, this could be interpreted as a penial caecum. The slender and relatively long retractor muscle inserts on the proximal end of the penis, slightly in proximal direction from the caecum; epiphallus also slender, slightly longer than the penis; vas deferens long and slim; vagina shorter than the penis and epiphallus combined, it is very thick, with a well-developed vaginal bulb; several short muscle fibres attach the vagina to the body wall and diaphragm; both the gametolytic sac and the diverticulum are very long and slim, although the gametolytic sac is somewhat thickened.

(Figures 19A–B): Radula elongated, but not very slender, central tooth present, laterals approximately 6, standing in straight lines (perpendicular to the central column); marginals approximately 14, although it is difficult to distinguish which are laterals and which are marginals; marginals are placed in oblique rows; central tooth wide-based triangular, smaller than the endocone of the first lateral, but much larger than the ectocone; laterals bicuspid, endo- and ectocones are triangular; marginals usually tricuspid (the endocone has two cusps), but some of the marginals are tetracuspid (both the endocone and the ectocone have two cusps); all cusps pointed, the incision between the innermost two cusps is deep.

Most museum samples have been collected in the Sikkim area. Gude received the holotype from Godwin-Austen, and it was said to be collected in the Naga Hills, approximately 600 km from Sikkim. The anatomically examined specimens have been collected from Silchar Cachar, which is located at least 500 km from Sikkim, but not far from the Naga Hills. If the samples from the Naga Hills and from Silchar are correctly labelled, we may expect that the species is widely distributed throughout north-eastern India (see also Figure 11).

Brahamakund, E. Assam, NHMUK 1903.7.1.751. (6 syntypes, Figure 16B).

Assam, leg. Hungerford, NHMUK 1891.3.17.362–364 (3 specimens); Assam, Brahmakund, coll. Godwin-Austen, NHMUK 20150144/27 (several shells juvenile); Brahmakund, NHMUK 20150145/8.

Shell very small, sinistral, with narrow umbilicus, depressed conical dorsally, conspicuous radial sculpture without hairs; callus very strong; palatal plicae short, straight, with many small denticles at their posterior ends, standing along a vertical line; lamella oblique, with three horizontal plicae anteriorly, the lowermost is in contact with the lower end of the lamella; besides these anterior plicae, there is a short upper plica above the lamella, and long lower plica close to the lower suture, which runs until the aperture.

(in mm): D: 8.1–8.2, H: 4.6 (n = 2, type series).

Endothyrella brahma can be distinguished from all other Endothyrella species by the presence of three parallel, horizontal parietal plicae anterior to the lamella. See also Table 5.

The species is known from the type locality only (Figure 10).

Nepal, Suridobhan, Dolakha, 1023 m, 27.758852°N, 86.197894°E, leg. Budha, P., 03.02.2009., holotype (CDZMTU001, Figure 14A), CDZMTU002 (2 paratypes = shells from the same locality); Nepal, Bhorle, Dolakha, 800 m, 27.696652°N, 86.129583°E, leg. Budha, P., 03.02.2009., 11 paratypes = shells (CDZMTU003).

Shell small with rather conical dorsal surface; body whorl slightly angulated with five rows of hairs; parietal lamella simple with one or two denticles posteriorly and a plica below; middle palatal plicae divided or almost divided.

Shell very small, sinistral, with somewhat elevated spire and rather conical apex; protoconch elevated from the dorsal surface; colour brownish or greyish; protoconch conspicuously large, consists of 2.25–2.5 whorls (n = 2), very finely, regularly ribbed; teleoconch with clearly visible reticulated sculpture dominated by radial growth lines; sculpture somewhat weaker on the ventral surface; very slender, long periostracal folds (hairs) standing in five spiral lines along the body whorl; whorls 5.25–5.5 (n = 3) moderately bulging, separated by relatively deep suture; umbilicus wide and deep; apertural lip whitish, thin, slightly reflexed; callus also very weak, slightly S-shaped; no fold in the aperture.

One specimen from the type locality was opened. Parietal wall with one rather straight lamella with slight lower arms pointing in both directions; small denticle near the upper end posteriorly, connected to the lamella; two short horizontal plicae under the lamella; palatal wall with six plicae; first slim and short, the second-fifth plicae are divided in the middle and are of the same length; last plica also short, rather straight (Figures 9G–H).

(in mm): D: 6.5–9.0, H: 4.0–5.0., Wh: 5.5–6.0 (n = 5).

The most similar species are E. affinis and E. plectostoma, which are larger, have a higher spire, and a deeper, narrower umbilicus. Endothyrella dolakhaensis sp. n. has a more elevated spire and more rounded body whorl than E. angulata sp. n. Moreover, E. dolakhaensis sp. n. has five rows of periostracal folds, whereas E. angulata sp. n. has four. See also under E. macromphalus, E. minor and E. nepalica sp. n. and Table 5.

The new species is named after the district name (Dolakha).

Nepal, Suridobhan, Dolakha, 1023 m, 27.758852°N, 86.197894°E.

Endothyrella dolakhaensis sp. n. is known from two localities in the valley of the Tamakoshi River, Dolakha district, Central Nepal (Figure 15).

Khasi Hills (?) from Fulton, NHMUK 1903.7.1.301. (2 syntypes, Figure 12A).

Ost-Ind., coll. Gerstenbrandt, NHMW 5954/2; Khasi Hills, Assam, coll. Rušnov, ex coll. Blume, NHMW 71770/R/9 (1 shell); Khasi Hills, leg. Godwin-Austen, NHMW 19599/2; India, Meghalaya, Khasi Hills, leg. Godwin-Austen, Altonaer Museum, ZMH 45907/2; Khasi-Berge, coll. Möllendorff, SMF 150103/3; Assam, Cherrapoonjeh, SMF 150104/4; Ostindien, Assam, coll. C. R. Boettger 1909, SMF 102818/1; Indien, Khasi Berge, coll. Bosch ex coll. Rolle, SMF 172070/3; Khasi Hills, coll. W. Blanford, NHMUK 1906.1.1.737/2; Khasi Hills, coll. Fulton, NHMUK 20150146/3; Assam, Khasi Hills, coll. Trechmann, NHMUK 20150147/2; Assam, Khasi Hills, NHMUK 1892.9.11.9–11/3 (one of them is small juvenile); Assam, Khasi Hills, coll. Lucas, NHMUK 20150148/2; Assam, Khasi Hills, coll. Smith, NHMUK 1937.12.30.13862–13864/3; India, Khasi Hills, coll. Salisbury ex coll. Beddome, NHMUK 20150149/2; Khasi Hills, Assam, coll. Gude, coll. Kennard, NHMUK 20150150/9; Assam, Cherrapoonje, coll. Lucas, NHMUK 20150151/1; no locality, dissected dried animal, NHMUK 20150152/3; no locality, coll. Jousseaume, MNHN 2012-27052/1 juvenile shell.

Shell middle sized to large, sinistral, with reversed trapezoid shape, narrow umbilicus, angled body whorl, an apex which is elevated from the dorsal surface, and four rows of hairs on the body whorls; callus very strong; 3rd, 4th and 5th palatal plicae are divided in the middle, the others are more or less straight and horizontal; lamella vertical or oblique, with short lower and upper plicae above and below.

(in mm): D: 19.9–20.3, H: 9.5–10.4 (n = 2, SMF 150103).

Endothyrella fultoni is much larger than any other Endothyrella species and has a characteristic reversed trapezoid shell shape. See also Table 5.

(Figures 21, 22B–C): A single specimen was anatomically examined. Collection data: Khasi, leg. Godwin-Austen, NHMUK 1903.7.1.598. The specimen had some embryos developing in the uterus. The whole body was very fragile, therefore the gametolytic sac and the diverticulum could not be dissected out.

The left ommatophoral retractor passes between penis and vagina. Atrium relatively long; penis long, consists of a longer, slimmer distal and a shorter, more thickened proximal part; at the proximal end of the penis there is a rounded bulb-like thickening (similar to that of some Gudeodiscus species, see Páll-Gergely and Asami 2014 and Páll-Gergely et al. 2015); penis internally with honey-comb-like tubercles without calcareous granules (Figure 22C); the somewhat slimmer penial caecum has some (approximately 8) parallel folds inside, which also form minute hollows standing in lines between the folds (Figure 22B); these small pockets may serve for small calcareous granules, although no granules were found; epiphallus enters penis at the basis of the rounded penial thickening; epiphallus relatively short, approximately as long as the proximal, thickened part of the penis; retractor muscle inserts on the proximal end of the penial caecum, it is approximately as long as the proximal part of the penis; vas deferens long and thick, it becomes curly near its insertion to the spermoviductus; vagina shorter than the the half of the penis; it has a vaginal bulb at the middle; two batch of fibres attach the proximal and distal part of the vaginal bulb to the body wall; there are also some longer and more slender muscle fibres attached to the vagina; between the atrium and the vaginal bulb there is a slender, longitudinal thickening on the inner vaginal wall; vaginal bulb internally with fine, irregularly reticulated sculpture; the area of the inner vaginal wall between the bulb and the spermoviductus is roughly reticulated; gametolytic sac relatively thick, the diverticulum is more slender.

(Figure 19C–D): The radula of the only available specimen was very fragile, probably because of the age of the sample; only a fragment of the middle part of the radula could be examined; central tooth present, laterals 14, marginals at least 8; central tooth very long, but somewhat shorter than the endocone of the first lateral, although larger than the ectocones; central tooth elongated triangular with slightly concave marginal line; endocone of the laterals are rather rhomboid, blunt, ectocone pointed triangular; endocones of marginals deformed rhomboid, sometimes oval, showing the sign of becoming bicuspid; ectocones of marginals blunt or pointed triangular.

The species is assumed to occur in the Khasi hills (Godwin-Austen 1892) (Figure 11).

Darjiling, coll. W. Blanford, NHMUK 1906.1.1.754. (holotype of macromphalus, Figure 23A); Yamne Valley, Abor Hills, leg. C.F.G. Oakes, R.E., NHMUK 1903.7.1.3124. (holotype of gregorsoni, Figure 23B).

Cherra, leg. Godwin-Austen, NHMUK 20150156/2 (juveniles, mixed sample with E. affinis); Khasi, leg. Stoliczka, 1880.xv.194., NHMW 92589/1 juvenile shell; Khasi Berge, SMF 150102/3 (mixed sample with E. minor); Khasi Berge, coll. Bosch, ex coll. Rolle, SMF 172069/2; Brit. Indien, Toruputu Dfola, 5000', coll. Ehrmann ex coll. Webb, SMF 150101/3; Dafla Hills, Burrail Gorge, coll. Godwin-Austen, NHMUK 1903.7.1.772/10 (4 had, 6 lacked a long lower plica); Khasi Hills, Mairang, coll. W. Blanford, NHMUK 1906.2.2.362/4 (3 lacked, 1 had a long lower plica); Khasi Hills, coll. Godwin-Austen, Figured in Godwin-Austen (1874), NHMUK 1903.7.1.766/9 (2 lacked, 7 had a long lower plica); Mairang, Khasi, NHMUK 1906.1.1.750/1; no locality, NHMUK 20150153/66 (19 shells had a long lower plica, 43 shells lacked, 4 corroded/dirty shells were not examined); Digny, coll. Godwin-Austen, NHMUK 20150154/1 (with long lower plica); Shillong, Khasi, “animal dissected”, NHMUK 1903.7.1.773/1 (with long lower plica); Teria Ghat, coll. Godwin-Austen, NHMUK 20150155/1 (with long lower plica); Toruputu Pk., Dafla Hills, NHMUK 1903.07.01.769/2 (mixed sample with E. minor); no locality, NHMUK 1871.9.23.68/4 (1 with, 3 without a long lower plica).

Shell very small, sinistral with relatively wide umbilicus, reticulated, almost flat spire (only the apex is elevated) and smooth umbilical side; callus weak, only very slight whitish lime layer is visible; palatal plicae straight, divided or not, lamella with short upper and lower plicae and two posterior denticles, one above and one below; the lower plica might be long (see under Additional material examined).

(in mm): D: 5.5–8.2.2, H: 2.7–4.2 (n = 13, shells from different samples); the holotype of Plectopylis gregorsoni is 7.5 × 3.7 mm.

Endothyrella macromphalus has more depressed shells than E. blanda. Moreover, E. macromphalus shells are smooth on the ventral side, whereas most blanda shells have hairs, or in case of corroded E. blanda specimens, holes which indicate the hairs’ positions. Endothyrella dolakhaensis sp. n. is hairy, has weaker sculpture, and its spire is more elevated than in E. macromphalus. Endothyrella robustistriata sp. n. is smaller, has a narrower umbilicus and stronger dorsal sculpture. See also under E. williamsoni and Table 5.

Endothyrella macromphalus seems to have a wide range including Assam and the Dafla and Khasi Hills. It has been reported from the Naga Hills, but those samples are probably misidentified. Plectopylis gregorsoni (treated here as a synonym of E. macromphalus) is recorded from the type locality only (approximately: 28°13.4'N, 95°13.3'E) (Figure 11).

The type specimen of Plectopylis gregorsoni is very similar to typical E. macromphalus specimens. The main difference is that the palatal plicae are not divided in gregorsoni, and the base is less glossy (rather weakly ribbed). In our view these minor difference are not sufficient for species level distinction, especially because E. macromphalus is a relatively variable species inhabiting wide geographical range. Very little is known about the distribution of specimens having divided or undivided palatal plicae. Therefore, until more information becomes available, Plectopylis gregorsoni is synonymised with Endothyrella macromphalus.

Darjiling, leg. Stoliczka, coll. Godwin-Austen, NHMUK 1903.07.01.768/10 syntypes. See also remarks.

Nepal, Lalitpur, Phulchowki Hill, 2308 m, 27.574557°N, 85.400842°E, leg. Budha, P., 04.05.2007., 21 shells (Figure 23F); Nepal, Kathmandu, Chisapani, Shivapuri-Nagarjun National Park, 2361 m, 27.804855°N, 85.436468°E, leg. Budha, P., 11.06.2007., 5 shells; Nepal, Golphubhanjyan, Langtang National Park, Rasuwa, 3340 m, 27.873931°N, 85.757744°E, leg. Budha, P., 10.06.2007., 1 shell; Nepal, Shivapuri-Nagarjun National Park, Deurali, Baghdwar, 2386 m, 27.798318°N, 85.385448°E, leg. Budha, P., 25.04.2008., 1 shell; Nepal, Shivapuri-Nagarjun National Park, Shivapuri Peak, 2707 m, 27.810987°N, 85.383763°E, leg. Budha, P., 24.04.2008., 1 shell; India, Darjiling, leg. Stoliczka, coll. Oberwimmer, NHMW 71640/O/6881 (4 shells); Darjeeling, coll. Rolle, NHMW 71770/R/11 (3 shells); Darjiling, coll. Dr. Stoliczka, 1880, NHMW 91587/20; Darjeeling, coll. Möllendorff, SMF 150112/2; Darjeeling, coll. Webb, SMF 150111/2; Khasi Hills, NHMUK 20150159/3; Sikhim, Rarhichu, NHMUK 20150158/6 (mixed sample with E. blanda); India, Darjeeling, coll. Oldham, NHMUK 20150160/5; India, 1879.12.26.172–177/5; Sikhim, NHMUK 1906.2.2.361/3; Darjeeling, NHMUK 20150161/1 (there is a number “751” on the bottom); Sikkim, NHMUK 1888.12.4.1525(?) (1 specimen); Darjeeling, under stones, 7000', coll. Everest Expedition 9 and 18.03.1924, NHMUK 20150162/5; Khasi Berge, SMF 345110/3 (ex E. macromphalus, SMF 150102); Toruputu Pk., Dafla Hills, NHMUK 1903.07.01.769/4 (mixed sample with E. macromphalus); Darjiling, coll. Hungerford ex coll. Nevill, NHMUK 1891.3.17.358–359 (Figure 23E).

Shell tiny, sinistral, with relatively narrow umbilicus, flat dorsal surface and four rows of hairs; callus strong; palatal plicae divided; lamella straight or slightly curved, with two denticles posteriorly, one above and one below; lower plica can be short and in some specimens reaching the peristome.

(in mm): D: 4.9–5.3, H: 2.4–2.6 (n = 3, type series); D: 5–5.1, H: 2.4 (n = 3, SMF 345110); D: 4–5, H: 2–2.5, Wh: 5–5.5 (n = 12, Nepalese specimens).

Endothyrella minor is smaller and has weaker keeled body whorl than E. angulata sp. n. Moreover, the first and second rows of the periostracal folds are comparatively at larger distance from each other in E. minor than in E. angulata sp. n. Endothyrella blanda has more elevated spire and more hair rows than E. minor. Endothyrella robustistriata sp. n. has more elevate spire than E. minor and lacks the hairs on its ventral surface. Endothyrella macromphalus is hairless and larger than E. minor, it has a comparatively larger protoconch and a lower (or missing) parietal callus. Endothyrella minor is smaller and flatter than E. dolakhaensis sp. n. Moreover, it has a more elevated parietal callus, and has only four rows of hairs (E. dolakhaensis sp. n. has five). See also under E. williamsoni and Table 5.

Originally the species was recorded from Darjeeling, Sikkim area. Very similar specimens were found from Central Nepal in the surroundings of Kathmandu (Shivapuri-Nagarjun National Park and Phulchowki hill) and Langtang National Park. Some literature records (Laisen Peak, Naga Hills) are based on misidentified specimens (see Figure 11 and 15).

W. Blanford (1870) described Helix (Plectopylis) macromphalus, and while giving information on its locality, he mentioned that “varietas minor” inhabits the Rungun valley near Darjeeling. No description or illustration of “varietas minor” was provided in the paper, therefore the name is not available. Later, Godwin-Austen (1879b) described Helix (Plectopylis) minor from “Darjiling hills” and mentioned those shell “no doubt are referable to P. macromphalus W. Blf., var. minor”. Blanford’s specimens labelled as macromphalus minor have not been found in the collection of the NHM, but the type sample examined and described by Godwin-Austen (NHMUK 1903.07.01.768) was found.

Recent fieldwork in Nepal yielded a few populations in the surroundings of Kathmandu which can be assigned to E. minor. “Typical” specimens of E. minor and Nepalese shells are very similar in terms of size, shell and aperture shape and the morphology of the plicae and lamellae. The only notable difference between these shells is the position of the hair rows on the body whorl. The first row is situated more upper in position (on the upper angle of the body whorl) in the Nepalese shells, whereas in typical shells the first row runs under the angle. Additionally, the distance between the third and fourth rows is smaller in the Nepalese populations.

Miri Hills, leg. C.F.G. Oakes, R.E., NHMUK 1903.7.1.3205. (4 syntypes, Figure 12C)

Shell small, sinistral, with very slightly elevated spire, relatively wide umbilicus, and conspicuous spiral sculpture; callus moderately strong, palatal plicae slightly oblique, connected by a vertical ridge; lamella almost straight, with anteriorly elongated upper and lower ends and small denticles on the posterior side, one above and one below.

(in mm): D: 12.1–12.3, H: 5.3–5.4 (n = 2, type series).

The unique spiral sculpture, which is very prominent on the ventral side as well, distinguishes E. miriensis from all congeners. See also Table 5.

The species is known from the type locality only (Figure 10).

Champadevi, Kirtipur, Kathmandu District, 1326–1500 m, 27.654868°N, 85.244084°E, leg. Budha, P., 02.10.2010., holotype (CDZMTU005.1), paratypes CDZMTU005.2–16 (15 shells), CDZMTU005P (2 paratypes = specimens dissected and preserved, 3 dry shells = paratypes, 2 juvenile shells = not paratype); W-Nepal, Dhaulagiri Zone, Myagdi District, Annapurna Conservation Area, right side of Kali Gandaki valley, 300 m NNW of Suke Bagar village along “Tatopani-Dana” track, 1430 m alt., 14.05.1996., leg. A. Kuznetsov, WM/10 paratypes; Nepal, Kathmandu Valley, NW end of Kathmandu, middle part of S slope of Swoyambhunath Hill, in dry oak forest, 1500 m, 25.04.1995, leg A. Kuznetsov, WM/4 sinistral and 1 dextral paratypes; W Nepal, Daulagiri zone, Hyagdi distr., Annapurna NP., right side of Kali Gandaki v., NNW od Suke Bagar, Tatop, leg. A. Kuznetsov, 14.05.1996., ex coll. W. Maassen, HNHM 95867/1 paratype (labelled as paratype of “Plectopylis nepalensis Schileyko and Kuznetsov”); Nepal, Swoyambhunath, Kathmandu District, 1366 m, 27.716971N, 85.289386 E, leg. Budha, P., 05.09.2008, CDZMTU006 (24 paratypes = shells); Siddha Cave, Tanahun District, 600 m, 27.94718°N, 84.421338°E, leg. Budha, P., 24.10.2008, CDZMTU004, CDZMTU007 (11 paratypes = shells, and one juvenile shell, which is not paratype) (Figs 6E, 24A); Dhunche, Rasuwa, 1985 m, 28.1092°N, 85.2916°E, leg. Budha, P., 31.05.2007., CDZMTU008 (2 shell = paratypes, and one damaged shell which is not paratype); Balaju, Kathmandu District, 1356 m, 27.741173°N, 85.293763°E, leg. Budha, P., 04.01.2009., CDZMTU009 (8 paratypes = shells), CDZMTU009P (2 paratypes = specimens preserved, 4 dry shells = paratypes); Mahadevsthan, Thankot, Kathmandu District 1500 m, 27.683366°N, 85.213834°E, leg. Budha, P., 06.02.2007., CDZMTU010 (25 paratypes = shells), CDZMTU010P 2 paratypes = specimens preserved, 4 dry shells = paratype, 5 juvenile shells = not paratypes); Arjewa, Baglung, 900 m, 28.154393°N, 83.630703°E, leg. Budha, P., 13.09.2006., CDZMTU011 (14 paratypes = shells, one juvenile shells = not paratype); Majhbeni, Parbat, 700 m, 28.205708°N, 83.674605°E, leg. Budha, P., 13.09.2006., CDZMTU012 (9 paratypes = shells, 6 juvenile/damaged shells = not paratypes); Sirsuwa, Parbat District, 780 m, 28.136478°N, 83.642135°E, leg. Budha, P., 13.09.2006., CDZMTU013 (6 paratypes = shells); Foksing, Parbat District, 790 m, 28.093252°N, 83.604283°E, leg. Budha, P., 11.06.2006., CDZMTU014 (11 paratypes = shells, 2 juvenile shells 7 not paratypes); Godawari, Lalitpur, 1868 m, 27.94718°N, 84.421338°E, leg. Budha, P., 01.10.2008., CDZMTU015a (1 paratype); Annapurna Conservation Area, Tatopani, 1282 m, 28.495172°N, 83.628883°E, leg. Budha, P., 01.10.2008., CDZMTU016 2 (2 paratypes = shells); Godawari, Lalitpur, 1575 m, 27.596459°N, 85.389432°E, leg. Budha, P., 30.06.2007., CDZMTU015b (1 paratype = shell); Ridi, Gulmi, 832 m, 27.945621°N, 83.43215°E, leg. Budha, P., 30.06.2007., CDZMTU017 (5 paratypes = shells); Godawari Botanical Garden, Lalitpur, 1453 m, 27.596671°N, 85.381758°E, leg. Budha, P., 03.09.2008., CDZMTU015c (50 paratypes = shells); Nepal, Pokhara, Khare, 1520 m alt., 28.2860°N, 83.8472°E, leg. C. Huber, 18.03.1991, NMBE 527538/1 paratype (Figure 24C).

A small to middle-sized, hairless species with domed dorsal surface and rounded body whorl; parietal lamella simple with one or two denticles posteriorly and sometimes a plica below the lamella, middle palatal plicae divided or almost divided.

Shell very small to small, sinistral, with somewhat elevated spire and domed dorsal surface; protoconch slightly elevates from the dorsal surface; usually brownish but sometimes turns into yellowish; protoconch consists of 1.5–1.75 whorls, very finely, regularly ribbed; teleoconch with very weak, irregular growth lines on the ventral surface and fine reticulated sculpture on the dorsal surface; in high magnification the surface is covered by flat periostracal folds; no spirally arranged large deciduous folds found; whorls 5.5–6.25, moderately bulging, separated by relatively deep suture; umbilicus wide and deep, whorls almost flat inside, resulting in an funnel-like shape, apertural lip whitish, rather thin, slightly reflexed; callus inconspicuous, but present, slightly S-shaped; no fold in the aperture.

Ten specimens were opened from different populations. Parietal wall with one slightly curved lamella with arms pointing in the direction of the aperture; lower end on the lamella more conspicuously curved than the upper end; two small denticles above and below posteriorly of the lamella (exceptionally, the lower one is missing); in some populations (e.g. Majhbeni – Parbat District, Champadevi – Kathmandu District and Siddha Cave – Tanahu District) with short plica under the lamella; palatal wall with six plicae; first slim and short, parallel with the suture; second plica is the longest, it shows a tendency towards dividing in the middle, but the two parts always fused; third, fourth and fifth plicae usually divided (third one sometimes not); last plica short, slightly curved with arms pointing in the direction of the lower suture (Figures 9C–F).

(in mm): D: 8.2–14.9, H: 4.0–6.0, Wh: 5.5–7.5 (n = 35, different populations).

Endothyrella nepalica sp. n. is usually larger than E. angulata sp. n., it has a domed dorsal surface, rounded body whorl and lacks hairs standing in spiral rows, whereas E. angulata sp. n. has a flat dorsal surface, shouldered body whorl and has hairs which are arranged in spiral rows. Endothyrella dolakhaensis sp. n. differs from E. nepalica sp. n. by the usually smaller size, fewer whorls, stronger sculpture, comparatively larger protoconch, conical dorsal surface, slightly angulated body whorl and the presence of hairs standing in five spiral lines. For comparison with E. oakesi and E. pinacis, see under those species. See also Table 5.

(Figures 25A–C): Three specimens from three populations were anatomically examined (Champadevi, Balaju of Kathmandu District and Godawari Botanical Garden, Lalitpur District). Penis short, narrow distally and slowly tapers toward the proximal end; internal surface with several tubercles including minute calcareous hooks; epiphallus slender, cylindrical, longer than the penis, it enters penis laterally; penial caecum very short, blunt, cylindrical, with a short retractor muscle attached at its proximal end; vas deferens thin and nearly 1.5 times longer than epiphallus, convoluted before connection to prostate; vagina shorter than the penis with well-developed vaginal bulb; gametolytic sac very thin throughout and ends into a small rounded sac; there is a slender diverticulum running parallel with the gametolytic sac; it is as long as the gametolytic sac.

The name nepalica refers to the country (Nepal) where the new species lives.

Champadevi, Kirtipur, Kathmandu District, Nepal, 1326–1500 m, 27.654868°N, 85.244084°E.

Endothyrella nepalica sp. n. inhabits a relatively large area in western and central Nepal (Figure 15).

Schileyko (1999) figured a shell from the “SW slope of Swayambhunat (= Swoyambhunath) hill, Kathmandu valley, Nepal” (Fig. 594.). The figured specimen is probably Endothyrella nepalica sp. n., but the drawing is not sufficient for identification.

Yamne Valley, Abor Hills, leg. C.F.G. Oakes, R.E., NHMUK 1903.7.1.3125 (5 syntypes, Figure 16A).

Sibbum, Abor, NHMUK, coll. Godwin-Austen, NHMUK 20150157/1; Abor Hills, “exact position not known”, below alt. 3000' between lat. 28°15'+29°15', long. 94°50'+95°10', leg. Oakes, coll. Godwin-Austen, NHMUK 1903.7.1.3125/1.

Shell small, sinistral, with wide umbilicus, and slightly domed dorsal surface; callus strong, palatal plicae complicated, their anterior part is horizontal, but the posterior part vertical; there are several short horizontal plicae between posterior parts of the palatal plicae; lamella almost straight with posteriorly elongated upper end, and sometimes with a long lower plica which reaches the aperture.

(in mm): D: 11.7–12.5, H: 4.7–5.5 (n = 3, type series).

Endothyrella nepalica sp. n. also has simpler palatal plicae than those of E. oakesi. Moreover, E. nepalica sp. n. has a flatter shell and a less descending aperture. See also under E. pinacis and Table 5.

This species was reported only from the localities mentioned in the original description (Yamne Valley, Abor Hills and Sibbum”, “between Riu and Singging, on the Dihang River”) (Figure 10).

Three specimens (two adults and a juvenile) of the type lot of E. oakesi were opened (probably by Gude). The long lower parietal plica, described as characteristic feature of this species, is present only in one specimen. In face of this, Endothyrella oakesi seems to be a distinct species on the basis of the palatal plicae and shell shape.

Sikkim, coll. Benson, UMZC 102755 (holotype of Helix pinacis, Figure 24D); Himalaya, ZMB/MOLL 17905 (holotype of Helix pettos, Figure 24E).

India, West Bengal, Darjeeling District, Lopchu + Ghum, coll. Topál, 21–22.04.1967, locality code: 869, HNHM 98848/2; Darjiling, coll. Dr. Stoliczka, 1880, NHMW 92590/7; Sikkim, coll. Möllendorff, SMF 150110/6 (3 of them juvenile); Darjeeling, coll. Bosch, ex coll. Rolle, SMF 172075/2; Darjiling, figured in Godwin-Austen (1874), coll. Godwin-Austen, NHMUK 1903.7.1.746/5; Darjiling, coll. W. Blanford, NHMUK 1860.6.27.14 (1 specimen); Kungna valy. (?) Sikm., NHMUK 20150163/2; Darjiling, NHMUK 1906.2.2.143/2 (Figure 24F); Damsang Peak, Daling Hills, coll. Godwin-Austen, NHMUK 20150164/26 (several of the juvenile); Sikkim, Rarhichu, NHMUK 20150165/5; Rechila Peak, coll. Godwin-Austen, NHMUK20150167/1; Darjiling, NHMUK 1888.12.4.1524/1; Darjeeling, 5000', coll. Everest Expedition 1924, NHMUK 20150168/1; Rarkichu, Sikkim, coll. Godwin-Austen, NHMUK 20150166/1.

Shell very small to small, sinistral, hairless, with wide umbilicus and slightly angulated body whorl; callus strong, palatal plicae short and oblique, lamella rather straight with anteriorly elongated upper and lower ends, and posteriorly elongated upper end; there are two denticles on the posterior side of the lamella, one above and one below, the lower one might be in contact with the lamella.

(in mm): D: 13.6–14.1, H: 5.9–6.1 (n = 3, SMF 150110).

Endothyrella angulata sp. n. is usually smaller than E. pinacis, it has a stronger keel and has weaker spiral lines on the ventral side of the shell, which are clearly visible in E. pinacis. The most similar species is Endothyrella nepalica sp. n., which nevertheless has a higher spire and rounded whorls, whereas E. pinacis has shouldered whorls and nearly flat dorsal surface. The ventral surface of the two species is similar, but E. pinacis has slender hairs standing in 3 lines, which is missing in E. nepalica sp. n. According to previous studies (Godwin-Austen 1889–1914, Schileyko 1999) E. pinacis has no diverticulum, but in all E. nepalica sp. n. we dissected that organ was present. Endothyrella oakesi is similar to E. pinacis, but has much more complicated palatal plicae, more descending aperture, differently shaped umbilicus and rounded body whorl. See also Table 5.

The anatomy of Endothyrella pinacis was described by Godwin-Austen (1889–1914) and Schileyko (1999). According to these descriptions, only the gametolytic sac is present and the diverticulum is missing. The penial caecum seems to be missing, although none of these drawings show this part clearly. Other features of the genitalia (penis shape, internal wall of the penis, vagina) are similar to those of E. nepalica sp. n.

Stoliczka (1871) mentioned that the central tooth is larger than that of Plectopylis achatina (= bensoni), and that its shape is similar to that of the laterals. Godwin-Austen (1889–1914) gave an accurate description and drawings of the teeth. According to his drawings the morphology of the teeth of E. pinacis is typical for the genus Endothyrella, i.e. the central tooth is larger than the ectocones of the first laterals, and the marginals are tricuspid with deep incisions between the two innermost cusps.

All museum samples examined were collected from Sikkim. Benson’s (1860) locality in the Khasi Hills is probably incorrect (Figure 11).

Darjeeling, coll. MacAndrew ex coll. Benson, UMZC 102160 (7 syntypes of plectostoma); Darjeeling, coll. MacAndrew ex coll. Benson, UMZC 102155 (1 syntype of plectostoma, Figure 13A); Bengal, coll. MacAndrew ex coll. Benson, UMZC 102156 (3 syntypes of plectostoma).

Indien, Khasi Hills, ex coll. Oberwimmer, NHMSB 122805–122810/5; India, Meghalaya, Khasi Hills, Altonaer Museum, ZMH 45909/4; Assam, coll. Steenberg, ZMUC-GAS-1812/2; Naraindher, Cachar, Ede, coll. Godwin-Austen, NHMUK 1903.7.1.1666/15 (several of them are juveniles); Darjiling, coll. W. Blanford, NHMUK 1860.6.27.10/2; India, NHMUK 20150169/1; Teria Ghat, NHMUK 1888.12.4.1536–1540/5; Pegu, coll. Godwin-Austen, NHMUK 1909.3.15.92/7; Naga Hills, coll. Godwin-Austen, NHMUK 1903.7.1.760/3; Pegu, Arakan, NHMUK 1903.7.1.758/3; Arakan, coll. W. Blanford, NHMUK 1909.3.15.60/3; Assam, Khasi Hills, coll. Salisbury ex coll. Beddome, NHMUK20150170/3; Lhota Naga, coll. Chennell, NHMUK 1903.7.1.759/10; Saddia, E Assam, coll. Godwin-Austen, NHMUK 1903.7.1.761/8; Picholanulla, Durrang, Assam, coll. Godwin-Austen, NHMUK 1903.7.1.763/1; Khasi Hills, coll. W. Blanford, NHMUK 1906.2.2.356.1–3 (3 shells; mixed sample with E. sowerbyi: 1906.2.2.356.4); Arakan, coll. W. Blanford, NHMUK 1906.2.2.355/4; India, NHMUK 20150171 (6 specimens); Darjiling, NHMUK 1906.2.2.142/1 (mixed sample with E. blanda); Shiroifurar, Lahupa Naga, coll. Godwin-Austen, NHMUK 1903.6.1.762/1; India, NHMUK 71.9.23.206/3; no data, coll. W. Blanford, NHMUK 20150172/2; Munipur valley, Bishenpur, west side, NHMUK 20150173/25 (several of them are juvenile shells); N. Cachar, coll. Godwin-Austen, NHMUK 20150174/2; Teria Ghat, coll. Godwin-Austen, NHMUK 20150175/1; Cherra, Khasi Hills, Assam, coll. Godwin-Austen, NHMUK 20150176/25; Dunsiri valley, coll. Godwin-Austen, NHMUK 20150177/4; Khasi Hills, coll. Godwin-Austen, NHMUK 20150178/68; Garo Hills, NHMUK leg. W. Robert, coll. Godwin-Austen, NHMUK 20150179/27; Burma, Bassein, coll. Benson 1863, NHMUK 1954.6.2.287/1; Khasi Hills, NHMUK 20150180/1 (mixed sample with E. tricarinata: NHMUK 20150181); Khasi Hills, NHMUK 20150182/3; Burroi Gorge, NHMUK 20150183/2; label not readable, NHMUK 20150185/7; Burrali, NHMUK 20150186/10; Khasi Hills, coll. Godwin-Austen, NHMUK 20150187/65; Khasi Hills, coll. W. Blanford, NHMUK 20150188/3; W. Khasi Hills, coll. Godwin-Austen, NHMUK 20150189/1; N. Khasi, coll. Godwin-Austen, NHMUK 20150190 (more than 100 shells); Khasi Hills, coll. Kennard, NHMUK/20150195/2 (mixed sample with E. tricarinata); Manipur, station 36, Godwin Austen Collection. NHMUK 20150191/87; Manipur, station 48, Godwin Austen Collection. NHMUK 20150192/58; Manipur, station 54, Godwin Austen Collection. NHMUK 20150193/119; Manipur, station 54, Godwin Austen Collection. NHMUK 20150194/89; Indien, leg. Stoliczka, coll. Oberwimmer, NHMW 71640/O/415 (2 shells; mixed sample with E. sowerbyi: NHMW 109252); Khasi Hills, leg. Stoliczka, 1870, NHMW 92588/3; Viaggio in Birmania (= trip to Burma), Shweego, coll. Fea, 1885–1889, NHMW 20034/4; Shwegoo, Birmania, leg. Mission L. Fea 1885–1889, MNHN 2012-27053/3; Khasi Hills, Himalaya, India, coll. Rušnov ex coll. Blume, NHMW 71770/R/13 (2 adult, 1 juv. shells); Ostindien, Pegu, leg. Stoliczka, coll. Edlauer, 477, NHMW 75000/E/4770 (1 shell; mixed sample with E. sowerbyi: NHMW 109253); Darjeeling, Himalaya, India, coll. Rušnov ex coll. Blume, NHMW 71770/R/14 (1 adult, 1 juv. shells; mixed sample with E. sowerbyi: NHMW 71770/R/15); Ostind., coll. Gerstenbrandt, NHMW 83901/G/2745 (2 shells); Pegu, ex coll. Hauer, NHMW 21617/4; Assam, coll. Landauer, NHMW 92594/2; Khasi Hills, Pegu (2 different label were found in the sample), coll. Stoliczka, NHMW 92591/41 (one of them is probably a juvenile E. tricarinata); Khasi, leg. Stoliczka, 1880, NHMW 92592/7; Khasi Hills, leg. Stoliczka, 1880, NHMW 92593/2 (mixed sample with E. sowerbyi: NHMW 109254 and E. blanda: NHMW 109255); East India, leg. Bernardi, Altonaer Museum, coll. O. Semper, ZMH 45908/1; Siam, Altonaer Museum, ZMH 45910/2; Birma, Moulmein, Hinterindien, coll. Krüper 1928, ex coll. Oberwimmer, SMF 118090/2 (mixed sample with E. sowerbyi: SMF 346406); Darjeeling, Himalaya, coll. Jetschin ex coll. Oberwimmer 1899, SMF 118088/1 (mixed sample with E. sowerbyi: SMF 346407); Khasi Hills, coll. Bosch, ex coll. Rolle, SMF 172072/1 (mixed sample with E. sowerbyi: SMF 346408); S-Shan Staaten, Ywathit, Prov. Karenni, a. mittleren Salwen, leg. Michelitz, SMF 150108/3; Indien, coll. Jetschin ex coll. Oberwimmer 1899, SMF 118089/2; Indien, Darjeeling, (alte Schau-sammlung), coll. Kobelt, SMF 150109/2; Khasi-Berge, coll. C. R. Boettger 1904, SMF 118091/1 (Fig. 13B); Assam, coll. Bosch, ex coll. Rolle, SMF 172071/4; Indien, Khasi-Hills, coll. Webb 1928, SMF 150086/2; Indien, Katschar, coll. Möllendorff, Orig. Handb. Pal. Fig. 2092; SMF 150106/4; Goramarah (Ghoramara), Chittagong, coll. Foulon 1936, MNHN 2012-27045/2; no locality, coll. Jousseaume, MNHN 2012-27050/3; no locality, coll. Jousseaume, MNHN 2012-27049/50.

A very small, sinistral species with very narrow umbilicus, conical dorsal surface, and hairs standing in five rows on the body whorl; palatal plicae more or less straight, the 4th and 5th divided; lamella slightly curved, with short lower and long upper elongation in anterior direction; there are two denticles posteriorly, one above and one below.

(in mm): D: 8.1–9, H: 4.6–5.1 (n = 3, SMF 172072).

Endothyrella plectostoma is similar to E. affinis and E. tricarinata in the narrow umbilicus. All other Endothyrella species of similar size have wider umbilicus. Endothyrella plectostoma is usually smaller, darker than E. affinis, it has a horizontal, relatively long plica anterior to the lamella, and has the periostracal folds arranged on five spiral line. In contrast, E. affinis lacks the horizontal parietal plica and has four hair rows. Moreover, E. plectostoma has a narrower umbilicus and more elevated spire than E. affinis. See also under E. sowerbyi and E. tricarinata and Table 5.

(Figures 22A, 22D–F, 26): Three specimens have been anatomically examined. Collection data: Sikhim, leg. Godwin-Austen, NHMUK 1903.7.1.451. All specimens had 5–6 embryos developing in their uterus. In one specimen no epiphallic differentiation was observed, the vas deferens started from the distal part of the penis (Fig. 22D).

The left ommatophoral retractor passes between penis and vagina. Atrium short; penis relatively short, internally with holes of various sizes; some tiny, rounded calcareous crystals were found in the penis lumen, not directly associated with the holes; this inner structure continued in the epiphallus; penial caecum short, with central thickening; retractor muscle short, it inserts on the proximal end of the penial caecum; epiphallus slightly longer than penis, it enters the proximal penial portion laterally; vas deferens long and slender; vagina approximately as long as the penis, but thicker, curved centrally; vagina with several thick and relatively long muscle fibres attaching it to the body wall and to the diaphragm, especially at its curved portion; vagina internally with longitudinal folds, which are rather sharp, elevated at the curved area of the vagina, and low elsewhere; the gametolytic sac and the diverticulum are aligned in parallel; the gametolytic sac is slightly thicker and shorter; a relatively long part of the spermoviduct was visible distal to the thickened uterus with the developing embryos; the embryo sac contained no visible calcareous granules, which were reported in other plectopylid species (Páll-Gergely and Hunyadi 2013, Páll-Gergely and Asami 2014); albumen gland conspicuously small. The latter trait is largely dependent on the period of the life cycle of the dissected specimen. In the present case, however, three specimens were anatomically examined and all specimens had a small albumen gland.

(Figure 19E–F): Radula elongated, but not very slender, central tooth present, laterals 8, standing in straight lines (perpendicular to the central column); marginals at least 14, staying in oblique rows; central tooth relatively narrow-based triangular, smaller than the endocone of the first lateral, but much larger than the ectocone; laterals bicuspid, endocone oval or narrow-based triangular; marginals tricuspid (the endocone has two cusps); all cusps pointed, the incision between the innermost two cusps is deep; in some cases the three cusps are almost of the same size.

Museum samples are labelled from several locations. This species is probably widely distributed in north-eastern India through south-eastern Bangladesh to Bago, the Arakan Hills and in the Kayah State in Burma (Myanmar) (Figure 7). A sample (ZMH 45910) was collected in “Siam” (= Thailand), which is possible because other samples were collected in Myanmar not far from the Thai Border.

The name “prodigium Benson” probably refers to Endothyrella plectostoma. It is a manuscript name, which was mentioned several times in the literature (Godwin-Austen 1875, Tryon 1887, Pilsbry 1894, Gude 1899c), but has never been published formally.

Munipur, Laisen Peak, coll. Godwin-Austen, NHMUK 1903.7.1.3453/1 (holotype, Figure 23D); Naga Hills, Ihang valley, coll. Godwin-Austen, NHMUK 1903.7.1.770/3 paratypes; Naga Hills, coll. Godwin-Austen, NHMUK 1903.7.1.767/3 paratypes (Figure 23C); Lhota Naga Hills, coll. Chennell, NHMUK 1903.7.1.765/4 paratypes.

A tiny species with elevated spire, smooth ventral side and strongly reticulated dorsal surface; parietal wall with a single lamella, an upper and a lower denticle posteriorly, and a long lower plica which reaches the peristome.

Shell tiny, sinistral, with slightly elevated spire and conical/domed dorsal surface; colour light brown, greenish or yellowish; protoconch consists of approx. 2 whorls, glossy, in some populations (NHMUK 1903.7.1.767, NHMUK 1903.7.1.770, NHMUK 1903.7.1.3453) only the last half whorl has a somewhat ribbed surface, whereas in another population (NHMUK 1903.7.1.765) nearly the whole protoconch is ribbed; dorsal surface of the teleoconch with clearly visible reticulated sculpture dominated by spiral lines; ventral side hairless, smooth, glossy, sometimes with radial growth lines; the ventral and dorsal surface change relatively abruptly above the middle line of the body whorls (from apertural = frontal view); inside the umbilicus there are sharp periostracal folds corresponding with radial ribs; whorls 4.5–4.75 (n = 3), slowly growing, separated by relatively deep suture; umbilicus narrow and deep; apertural lip whitish, thickened, normally not reflexed, or reflexed only near the umbilicus; callus very weak, nearly invisible in case of fresh shells, in case of old, corroded shells it becomes white; aperture without entering fold.

Two opened specimens were observed (NHMUK 1903.7.1.767 and NHMUK 1903.7.1.765). Parietal wall with one rather straight lamella which bends anteriorly; it has both the upper and lower ends elongated anteriorly; two small denticles visible at the posterior side of the lamella, one above and one below; lower plica very long, reaches the peristome; palatal wall with six plicae; first slim and short, the second–fifth plicae horizontal; they do not seem to be divided if we observe through the translucent shell wall, but their middle portion (where the lamella is present on the parietal wall) is much lower; the posterior ends of the middle plicae slightly bent downwards, whereas the anterior parts are straight and horizontal; the last plica is short and slightly curved (Figure 9K–L).

(in mm): D: 4.1–4.6, H: 2.3–3.5 (n = 2 NHMUK 1903.7.1.765).

Endothyrella blanda is similar in shell shape to E. robustistriata sp. n., but is larger, has hairy ventral surface (or if hairs are missing, than hollows are visible indicating the hairs’ positions), and on its dorsal surface the radial lines are dominant. See also under E. macromphalus and E. williamsoni and Table 5.

The word robustistriata means strongly striated (Latin) which refers to the prominent spiral striae of the new species on the dorsal side of its shell.

Munipur, Laisen Peak.

The new species is known only from the Naga Hills and Manipur (Figure 11).

Khasia Hills, India, NHMUK 1922.8.29.48. (holotype, Figure 13C).

Indien, leg. Stoliczka, coll. Oberwimmer, NHMW 109252/2 (mixed sample with E. plectostoma: NHMW 71640/O/415); Ostindien, Pegu, leg. Stoliczka, coll. Edlauer, 477, NHMW 109253/7 (mixed sample with E. plectostoma: NHMW 75000/E/4770); Darjeeling, Himalaya, India, coll. Rušnov ex coll. Blume, NHMW 71770/R/15 (3 shells; mixed sample with E. plectostoma: NHMW 71770/R/14); Khasi Hills, leg. Stoliczka, 1880, NHMW 109254 (approx. 70 shells; mixed sample with E. plectostoma: NHMW 92593 and E. blanda: NHMW 109255); Khasi Hills, coll. W. Blanford, NHMUK 1906.2.2.356.4 (3 shells; mixed sample with E. plectostoma: NHMUK 1906.2.2.356.1–3); Darjeeling, 3500', leg. Lister, NHMUK 1907.9.13.11–22/11; Birma, Moulmein, Hinterindien, coll. Krüper 1928, ex coll. Oberwimmer, SMF 346406/2 (mixed sample with E. plectostoma: SMF 118090); Khasi Hills, coll. Bosch, ex coll. Rolle, SMF 346408/5 (mixed sample with E. plectostoma: SMF 172072) (Fig. 13D); Khasi Hills, coll. Jetschin, ex coll. Linter 1893, SMF 118087/1; Darjeeling, Himalaya, coll. Jetschin ex coll. Oberwimmer 1899, SMF 346407/2 (mixed sample with E. plectostoma: SMF 118088).

A very small, sinistral species with narrow umbilicus (but wider than in the three similar species; affinis, plectostoma, tricarinata), rather domed dorsal surface, and hairs standing in five rows on the body whorl; the hairs are usually missing and the ventral side is with relatively strong radial lines; plication similar to E. plectostoma, but the main anterior parietal plica is missing or weak.

(in mm): D: 7.8–8.6, H: 4.3–5.0 (n = 3, SMF 346408).

Endothyrella affinis is larger, has lighter shell with narrower umbilicus and a weaker sculpture. Endothyrella sowerbyi has a wider umbilicus and a thinner peristome than E. plectostoma. Moreover, the spire is lower and the dorsal side is rather domed in E. sowerbyi (conical in plectostoma), and the main parietal plica is weaker or missing. See also under E. tricarinata and Table 5.

Museum specimens are collected from the Khasi Hills, Darjeeling, and Burma.

During the preparation of this revision, Endothyrella sowerbyi was handled as the synonym of E. plectostoma, because the only known specimen (the holotype) looked like a juvenile shell of E. plectostoma. The first author recognized that E. sowerbyi is a valid species in the Senckenberg Museum in August, 2015, because of several mixed samples deposited there. Thus, the Endothyrella plectostoma/sowerbyi sample of the SMF were identified and the E. sowerbyi shells were separated by B. Páll-Gergely. The E. plectostoma samples in the NHM were checked by Jonathan Ablett, whereas those in the NHMW were examined by Zoltán Fehér.

Bengal, coll. MacAndrew ex coll. Benson, UMZC 102170 (2 syntypes of Plectopylis plectostoma var. tricarinata, Figure 13E); Khasia Hills, ex Nissor (?), NHMUK 1922.8.29.50. (syntype of Plectopylis plectostoma var. exerta, Figure 13F).

India, Khasia Hills, K4.30, coll. Rolle, NHMW 50854/2; Assam, Khasia Hills, coll. Bosch, ex coll. Rolle, SMF 172073/3; Assam, Cherrapoonjee, coll. Jetschin, ex coll. Gude 1900, (labelled as syntype, but it is probably not), SMF 118097/1; Assam, coll. Ehrmann ex coll. Schlüter, SMF 150113/1; Khasi Hills, figured in Godwin-Austen (1874), NHMUK 1903.7.1.757 (note that in the original sample it is erroneously 759) (11 specimens under the name affinis); Khasi Hills, coll. W. Blanford, NHMUK 1906.1.1.743/2; Khasi Hills, India, Assam, NHMUK 1916.3.16.6–7/2; Khasi Hills, coll. Kennard, NHMUK 20150181/2 (mixed sample with E. plectostoma see NHMUK 20150180); Khasi Hills, NHMUK 20150196/2 (mixed sample with E. plectostoma); Khasi Hills, Assam, ‘Preston’, V.W. MacAndrew Collection (Acc. No.1563), NHMUK 20150197/3; Khasi Hills, Bengal, ‘Rolle, C/R June 03', V.W. MacAndrew Collection (Acc. No.1563), NHMUK 20150198/2; Khasi Hills, India, ‘Rolle, C/R 8/5/13', V.W. MacAndrew Collection (Acc. No.1563), NHMUK 20150199/2.

A small, sinistral species with narrow umbilicus, conical dorsal surface with strong spiral lines, strongly, densely ribbed surface, and hairs standing in four rows on the body whorl; palatal plicae more or less straight, they are more or less divided; lamella slightly curved, with small denticles on the posterior side (they might fuse to the lamella), and a long upper plica on the anterior side of the lamella.

(in mm): D: 10.1–10.4, H: 6.3–6.7 (n = 2, SMF 172073).

Endothyrella affinis has less shouldered whorls, wider umbilicus, weaker sculpture and it lacks the long horizontal plica anterior to the lamella. Endothyrella tricarinata differs from E. plectostoma by the larger size, more conical dorsal surface, narrower umbilicus, the shouldered whorls, the presence of only four rows of hairs, and the stronger sculpture. Endothyrella sowerbyi has much weaker dorsal sculpture and has wider umbilicus. See also Table 5.

All museum samples were collected from the Khasi Hills and Assam (Figure 11).

Two varieties of Plectopylis plectostoma have been described under the names Plectopylis plectostoma var. tricarinata and P. plectostoma var. exerta. Both of them differ from typical Endothyrella plectostoma specimens by the more shouldered whorls, and the more conical dorsal side of the shell having stronger spiral lines. No difference between the type specimens of these forms have been found except for the presence (exerta) and the absence (tricarinata) of hairs. The absence of hairs might be due to the corroded state of the syntypes of tricarinata. Although the difference between typical E. plectostoma and typical tricarinata/exerta shells seem to be minor, we found no intermediate forms, and in some cases we found mixed museum samples which indicate that the shells might have been collected from the same site. This suggest that Endothyrella plectostoma and E. tricarinata are distinct species.

Abor Hills, leg. C.F.G. Oakes, R.E., NHMUK 1903.7.1.3087. (5 syntypes, Figure 17A)

Shell very small, sinistral with narrow umbilicus and conical dorsal surface; shell hairless but densely, finely ribbed and ornamented with low radial periostracal lamellae on the whole shell; callus strong; palatal plicae horizontal, almost straight and thin at their middle; lamella slightly curved; there is long, horizontal plica anteriorly to the lamella, and a short horizontal plica above the long one; additionally, there is a very short upper plica above the lamella, a small denticle posteriorly above, and a long lower plica near the suture which reaches the aperture.

(in mm): D: 6, H: 3.6–3.7 (n = 2, type series).

Endothyrella williamsoni has a more elevated spire than E. macromphalus and E. minor, and has two horizontal parietal plicae anterior to the lamella which are missing in the other two species. The most similar species in terms of shell shape and size to E. williamsoni is E. blanda. The latter species, on the other hand, lacks the two horizontal parietal plicae anterior to the lamella which area characteristic for E. williamsoni. Moreover, E. blanda specimens have seven rows of hairs, whereas E. williamsoni is hairless. Endothyrella robustistriata sp. n. is smaller, has stronger dorsal sculpture and lack the main plica which is characteristic for E. williamsoni. See also Table 5.

This species is known from the type locality only (Figure 10).

“Shell sinistral, depressedly conoid, openly umbilicated, probably hirsute when young. Sculpture coarse, irregular, transverse ridges. Colour uniform ochraceous. Spire conoidal; apex blunt, smooth. Suture well marked. Whorls six, close-wound, convex. Aperture semicircular, diagonal; peristome somewhat thickened, white, with a thin callus on the parietal margin, not to the extent of a ridge. Size — major diam. 5.5, minor diam. 5.0, alt. 3.0 millims. Parietal vertical lamina simple; palatal plicæ in two rows, four long in front, four short behind, and one basal long. The shell is very distinct; it has somewhat the form of P. plectostoma, but is not so angular on the periphery, while the internal plication is quite different, besides being so very much smaller in size.”

In the original description Godwin-Austen (1879b) wrote that the holotype is “in the collection of Mr. Sylvanus Hanley”. In Godwin-Austen’s copy of Gude (1914, page 77), Godwin-Austen has written “In my collection”. The holotype, however, was not found in the collection of the NHM. Only one NHM specimen was found labelled Plectopylis hanleyi, and this is annotated with a question mark (“Sikkim, Rarhichu, H. H. Godwin-Austen colln.”). However, this specimen is very similar to the type specimen of Plectopylis blanda, and is not identical with the single shell in Godwin-Austen’s (1879b) description, because it has only 4.75 whorls (the holotype of P. hanleyi has six). Moreover, Godwin-Austen (1879b) described the palatal lamellation, whereas the above mentioned specimen is intact, therefore the inner lamellae and plicae could not be observed. Some parts of Hanley’s collection are housed in the Leeds Museum and in the Manchester Museum. The former were contacted and confirmed that the holotype was not deposited there. The catalogue of the type specimens of the Manchester Museum (McGhee 2008) did not list Plectopylis hanleyi. Since the holotype of Plectopylis hanleyi seems to be lost, and the description is not sufficient to diagnose the species (although it matches with E. blanda), P. hanleyi is considered to be a nomen dubium.