Radiolucina cancellaris (Philippi 1846)

Shell shape. Subovate, inflated; maximum length: 7.2 mm, maximum height: 8.0 mm; beaks prosogyrate. Sculpture and color. Average 12 (10–15 n=76) non-bifurcating radial ribs, overlain by thin commarginal lamellae that continue through interspaces, producing a reticulate pattern; interspaces sunken, thin towards beak, progressively widening ventrally; anterior end smooth, with fine commarginal striae; posterior end with a series of average 13 (12–15 n=20) thick spines of varying heights protruding from shell; inner ventral margin crenulations thin, closely spaced; interior color white to cream, shiny. Hinge. Hinge plate thick, straight with slight curve; cardinal teeth small, right valve posterior thin, anterior thick, left valve middle tooth wide; lateral teeth large, posterior vertical, anterior horizontal;ligament sunken above the cardinal teeth. Adductor scars and pallial line. Pallial line discontinuous, broken into small and large segments, with one small circular indentation directed ventrally; anterior adductor scar large, narrow, diverging from pallial line for about a quarter of its length; posterior adductor scar small, wide, pallial line joins at most ventral point.

Known from Isla Cedros, Pacific coast of Baja California (28.2°N) [Keen, 1971], into the Golfo de California as far north as near its head at Puerto Peñasco, Sonora (31.3°N) [LACM], México, to Isla San Lorenzo, Lima, Perú (12.1°S) [LACM]; intertidal zone to 212 m [LACM]. Also in the Pliocene of Ecuador and the Pleistocene of Baja California.