Genus Curvella Chaper, 1885

Bulimus (Hapalus) Albers, 1850: 140. [non Illiger 1801 (Coleoptera)]. Type species Bulimus grateloupi Pfeiffer, 1846 . Albers 1860: 238.

Curvella — Chaper, 1885: 49. Pilsbry 1906: 46. Gude 1914: 348. Zilch 1959: 351. Schileyko 1999: 515. Budha et at. 2017: 120.

Type species.

Curvella sulcata Chaper, 1885, by original designation in Chaper (1885: 48).

Diagnosis.

Shell oblong-conical; spire low or high and rapidly attenuated; embryonic whorls smooth; subsequent whorls with equally or irregularly spaced thick or fine radial striations or ribs. Aperture vertical, broad-ovate, or oblong, and somewhat pointed above; columella straight; columellar margin expanded near umbilicus. Penis simple and short papillate or short tube; epiphallus and flagellum absent; vagina large, muscular, and nearly equal to penis length.

Remarks.

Curvella is clearly distinct from other subulinid genera such as Allopeas, Bacillum, and Opeas by its oblong-conical shell, short spire, high and wide aperture, and its much broader last whorls (Table 2). Regarding the genitalia, this genus displays a more rounded, muscular, short penis and a thicker vagina than Allopeas and Opeas (Schileyko 1999) . In comparison, the two latter genera have a slender, narrow, more elongated penis and vagina compared to Curvella (Schileyko 1999; Budha 2017). However, only genitalia of Curvella sikkimensis (Reeve, 1850) is known for this genus at present (Budha 2017).

This genus is widely distributed from Africa to South Asia and China, and ~ 95 species have been reported (Pilsbry 1906; Gude 1914; Schileyko 1999; Ramakrishna et al. 2010; Budha et al. 2017; MolluscaBase 2023). There are scattered reports of four Curvella species in Myanmar, while one species, C. tonkiniana Jaeckel, 1950, has been reported in Vietnam and one species, C. jousseaumei (de Morgan, 1885), from Peninsular Malaysia (Gude 1914; Maassen 2001; Schileyko 2011; Vermeulen et al. 2015).