Rishetia burrailensis maxwelli ( Godwin-Austen, 1920 )

Man, Nem Sian, Ablett, Jonathan D., Lwin, Ngwe, Sutcharit, Chirasak & Panha, Somsak, 2024, Contributions on a small collection of the former Subulinidae Fischer & Crosse, 1877 (Eupulmonata, Achatinoidea) with catalogue of the Glessula and Rishetia species recorded from Myanmar, ZooKeys 1208, pp. 173-239 : 173-239

30 Rishetia burrailensis maxwelli ( Godwin-Austen, 1920) comb. nov.

Figs 13 G – I , 14 A – C

Glessula (Rishetia) burrailensis, var. maxwelli Godwin-Austen, 1920: 45, 46, pl. 160, figs 5, 6. Type locality: Naga Hills, east of Kohima and Somra, Khulen Post. West of Kyendwin or Chindwin River, Upper Burma.

Glessula burrailensis, var. maxwelli — Godwin-Austen 1920: 61. Type locality: Somra Tracts, Somra Khulen Post, Upper Burma.

Type specimens.

Holotype NHMUK 1903.7. 1.1717 / 1 (Fig. 13 G ) ex. Godwin-Austen collection from Naga Hills , East of Kohima . Paratypes NHMUK 1903.7. 1.1717 / 2–4 (3 shells; Fig. 13 I ) ex. Godwin-Austen collection from the location same as the holotype .

Other material.

NHMUK 1903.7. 1.3742 (7 shells + 1 broken shell; Fig. 14 A, B ) collected by F. Ede ex. Godwin-Austen collection from Somra Tracts, Somra Khulen Post, Burma (labelled as ‘ var. somraensis ’). NHMUK 1903.7. 1.3744 (2 shells; Fig. 14 C ) collected by F. Ede ex. Godwin-Austen collection from Somra Tracts, Somra Khulen Post, Burma (labelled as ‘ var. somraensis ’). NHMUK 1988147 (4 shells; Fig. 13 H ) collected by L. R. Mawson from Somra Tracts, Somra Khulen Post, west of Kyengdwen River, Burma.

Diagnosis.

Shell elongate, turreted, and regularly attenuated; apex rounded and blunt; subsequent whorls nearly smooth with fine irregularly spaced radial ridges throughout, and coarser ridges appearing near suture. Suture impressed and whorls flattened. Aperture ovate; columella concave and truncated.

Distribution.

This subspecies was originally described from the Naga Hills. The locality reported in Myanmar is Somra Town (~ 25 ° 21 ' 43.6 " N, 94 ° 41 ' 14.4 " E), a mountainous area in Leshi or Layshi Township, Sagaing Region in northwestern Myanmar. It is neighbouring Nagaland to the west and Kachin State to the east and along the Chindwin River.

Remarks.

The name maxwelli was stated twice in the same publication, on pages 45 and 61. The first mention is ‘ Glessula (Rishetia) burrailensis, var. maxwelli ’; when proposing this name, Godwin-Austen (1920: 45) recognised two specimen lots from Naga Hills … (collected by Col. H. St. P. Maxwell) and from Somra … Upper Burma (collected by F. Ede). Although the species description is brief, Godwin-Austen provides the catalogue number ‘ No. 1717 B. M. ’, two sets of shell dimensions, and illustrations of two shells from Naga Hill. We have examined this specimen lot, NHMUK 1903.7. 1.1717, from Naga Hills, which consists of four shells. In the original description, Godwin-Austen (1920: 46) further states, ‘ Size: Fig. 5 . Type’ and in the figure caption as ‘ Fig. 5 . (1 st Type) from Naga Hills’ and ‘ Fig. 6 . (2 nd Type) from Naga Hills’. It seemed that Godwin-Austen intended to designate the specimen figured in plate 160, fig. 5, as the unique name-bearing type, which we consider as the holotype. The other three specimens from the same lot are therefore paratypes.

The second mention is ‘ Glessula burrailensis, var. maxwelli ’, for which Godwin-Austen (1920: 61) provided a very detailed description together with specimen lot number ‘ No. 3742 B. M. ’, two sets of shell measurements, from ‘ Somra Tracts, Somra Khulen Post, Upper Burma, but without illustration. The NHMUK collections contain specimen lot NHMUK 1903.7. 1.3742, consisting of eight specimens with the original label stating ‘ var. somraensis, GA. ’. This manuscript name has never properly been published and made available ( ICZN 1999: Art. 10), the specimen lot NHMUK 1903.7. 1.3742, with its original label stating ‘ var. somraensis ’ is considered as the syntype. Therefore, this second combination becomes an available name ( ICZN 1999: Arts 11, 12), and it is considered a junior (primary) homonym ( ICZN 1999: Arts 24.2. 1, 24.2. 2, 53.3, 57.2). Additionally, syntypes also include, NHMUK 1988147 (4 shells), from Somra, Khulen Post, West of Kyendwin River, Upper Burmah, as Godwin-Austen (1920: 61) recognised in the original description.

After examining the type specimens carefully, we found no differences in the diagnostic characters between the senior homonym ( NHMUK 1903.7. 1.1717 / 1 and NHMUK 1903.7. 1.1717 / 2–4) and junior homonym ( NHMUK 1903.7. 1.3742, NHMUK 1903.7. 1.3744 and NHMUK 1988147) specimens, especially shell shape, shell sculpture, and protoconch sculpture. The only detected difference is the brownish or yellowish brown periostracum, which we consider as intraspecific variation. Therefore, it seems unnecessary to propose a new replacement name for this junior homonym.

Figures

Figure 5. A – D Glessula blanfordiana A, B syntypes NHMUK 1988150 from Ponsee, Yunnan, W. China and C, D specimen CUMZ 13067 from Taunggyi, Shan State, Myanmar E, F Glessula crassilabris E syntype UMZC I. 102430 from Bengal (after Preece et al. 2022: fig. 51 e) and F specimen NHMUK from Cherrapoonji (M 10604 / 2).

Figure 6. A – F Glessula feddeni A, B syntypes NHMUK 1906.2. 2.261 from Shan Hills, E. of Ava C specimen NHMUK 1906.3. 3.41 from Shan Hills and D – F specimen CUMZ 13068 from Pyinyaung Village, Mandalay Region, Myanmar.

Figure 13. A – C Rishetia akouktoungensis, syntypes NHMUK 1906.1. 1.2207 from Akouktoung, Pegu D Rishetia baculina, syntypes NHMUK 1909.3. 15.9 from Kursiong, Darjiling E, F Rishetia basseinensis, syntypes NHMUK 1909.3. 15.19 from Bassein G – I Rishetia burrailensis maxwelli G holotype NHMUK 1903.7. 1.1717 / 1 from Naga Hills, East of Kohima H specimen NHMUK 1988147 from Somra Tracts, Somra Khulen Post, west of Kyengdwen River, Burma and I paratypes NHMUK 1903.7. 1.1717 / 2–4 from Naga Hills, East of Kohima.

Figure 14. A – C Rishetia burrailensis maxwelli A, B specimen NHMUK 1903.7. 1.3742 from Somra Tracts, Somra Khulen Post, Burma and C specimen NHMUK 1903.7. 1.3744 from Somra Tracts, Somra Khulen Post, Burma D Rishetia hastula, neotype NHMUK 1906.1. 1.880 from Darjiling E, F Rishetia kentungensis, syntypes NHMUK 1903.7. 1.3650 from Mong Sing, Siam Boundary G Rishetia limborgi, holotype NHMUK 1903.7. 1.3200 from Tenasserim H, I Rishetia nathiana, syntypes NHMUK 1906.1. 1.2206 from Bassein District.