Genus Omalogyra Jeffreys, 1859b

Omalogyra Jeffreys, 1859b, p. 498 . Type species by subsequent designation of Bucquoy et al. (1884, p. 78): Truncatella atomus Philippi, 1841, p. 54, pl. 5, figs 4a–d.

Ammonicerina O. G. Costa, 1861, p. 67. Type species by subsequent designation of Dall (1927, p. 134, as “Ammonocerina”): Ammonicerina simplex O. G. Costa, 1861, p. 72, pl. 11, figs 3a, b.

Homalogyra Jeffreys, 1867, p. 67 (unjustified emendation).

Helisalia Laseron, 1954, p. 16 . Type species by original designation: Helisalia liliputia Laseron, 1954, pp. 16–17, figs 45,45a.

Diagnosis. Shell extremely minute; protoconch smooth or finely nodulose, devoid of conspicuous axial or spiral sculpture; sculpture of the teleoconch weak or absent; aperture rounded; each radular row composed of a single dagger-like tooth, flanked by one lateral plate on each side [formula 0-(1)-1-(1)-0]; cephalic tentacles forming rounded lobes.