Bacillum Theobald, 1870

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

Genus Bacillum Theobald, 1870

Achatina (Bacillum) Theobald in Hanley and Theobald 1870: 17.

Bacillum — Pilsbry 1906: 1. Gude 1914: 343. Godwin-Austen 1920: 7. Zilch 1959: 346. Schileyko 1999: 534.

Type species.

Achatina cassiaca Reeve, 1849 a , subsequent designation by Pilsbry (1906: 1).

Diagnosis.

Shell slender and conical in shape; spire high, turreted, and gradually attenuated; embryonic whorls cylindrically rounded, and with or without radial striations; subsequent whorls with equally spaced thick or fine radial striations. Aperture oblique and narrowly ovate; columella concave and truncated, and columellar margin simple or slightly expanded.

Remarks.

Bacillum can be differentiated from Allopeas in being cylindrically rounded and with striations on the embryonic whorls, whilst the columella is concave and truncated ( Pilsbry 1906; Schileyko 1999). While Allopeas has a narrowly attenuated and smooth embryonic whorls, columella straight, and columellar margin near umbilicus expanded (Table 2 ).

At present, this genus contains seven species mainly distributed in India, and among these, two species are known from Myanmar ( Blanford 1869; Pilsbry 1906; Gude 1914; Ramakrishna et al. 2010; MolluscaBase 2023). All Bacillum species are known only from shell morphology, and none of the reproductive anatomy has been published so far. Godwin-Austen (1920) stated, ‘ … extended knowledge of the animals of Bacillum and Glessula shows that the two genera come next each other … ’, which suggests Godwin-Austen had dissected Bacillum , but his findings were never published.