Opeas Albers, 1850

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 Opeas Albers, 1850

Bulimus (Opeas) Albers, 1850: 175, 176.

Stenogyra (Opeas) — von Martens 1860: 265, 266.

Opeas — Fischer and Crosse 1877: 592. Pilsbry 1906: 122. Gude 1914: 354. Zilch 1959: 351, 352. van Benthem Jutting 1952: 378. Schileyko 1999: 492.

Type species.

Helix goodallii Miller, 1822 [junior homonym of Férussac (1821)] accepted as Opeas hannense ( Rang, 1831) , subsequent designation by von Martens in Albers (1860: 265).

Diagnosis.

Shell small, slender, and conical; spire high, turreted, cylindrically, and gradually attenuated; embryonic whorls smooth; subsequent whorls with fine radial striations or growth lines. Aperture vertical, narrow, oblong, columellar margin expanded, and columella straight or concave. Umbilicus narrowly opened or closed. Penis cylindrical tube with short epiphallus, and flagellum and penial sheath absent; vagina long ~ 1 / 2 of penis length.

Remarks.

Opeas and Tortaxis Pilsbry, 1906 generally resemble one another in having slender conical or cylindrical shells, nearly smooth to fine striations, and flatly convex whorls (Table 2 ). However, Opeas has a smaller size, straight columella, and mostly oblong aperture, whereas Tortaxis displays mostly larger size, nearly straight or slightly concave columella with a spiral fold, and more or less obliqued aperture. Likewise, Opeas is distinctly differentiated from Bacillum in that it is smaller in size, has a straight columella, fine shell sculptures and embryonic whorls which are narrowly rounded. In contrast, Bacillum exhibits a larger shell size, truncated and concave columella, stronger shell sculptures, and the embryonic whorls cylindrically rounded.

This genus is distributed in tropical and subtropical regions in Europe, Asia, Africa, and North America, and comprises nearly 200 species ( Schileyko 1999; MolluscaBase 2023). In Myanmar, two species are recorded ( Gude 1914).