Diagnosis: Shell small, conical, peripherally bicarinate, umbilicate, nacreous under thin outer porcelarieous layer, white; protoconch large; first 0.5 whorl lacking spiral sculpture, subsequent whorls with strong cord above periphery and strong peripheral cord together forming weakly bicarinate periphery, weak to strong spiral cords on base, and strong, smooth or pustulate circum-umbilical cord; axial sculpture of obscure, sigmoid folds and growth lines; surface microsculpture of microscopic, shallow punctae; base weakly convex; umbilicus narrow, funnellike; aperture subquadrate; labral sinuses 2, wide, shallow ; columella straight or weakly concave. Radula unknown.
Remarks: Asthelys most closely resembles Thelyssina Marshall, 1983. Shells of both genera are conical with almost flush sutures, lack a mid-whorl carina, spiral cord, or angulation on the first teleoconch whorl immediately following the termination of the protoconch, lack strong collabral and spiral microsculpture above the whorl periphery, and have a narrow, funnellike umbilicus. The type-species of Asthelys differs from that of Thelyssina by lacking a trochoid tip and terminal rim on the protoconch, having minute punctae instead of vermiculate microsculpture on the first two spire whorls (although T sterrha Marshall, 1983, also has punctations, fide Marshall, personal communication), having a bicarinate rather than unicarinate periphery, having a distinct posterior shell sinus, persistence of the initial spiral cord on all teleoconch whorls, and lacking a strong parietal callus. At least two other species may also be assigned to Asthelys: Basilissa simplex Watson, 1879, and an undescribed Antarctic species (Marshall, personal communication).