Shell small, not very heavy, acutely high-conic; aperture ovate; apex a little in front of center; both anterior and posterior slopes nearly straight, sometimes flaring toward margin; exterior sculptured with 13 or 14 flat broad rude subtuberculate radial ribs, plus 1 to 3 narrower riblets in the interspaces, the major ribs frequently imperfectly sulcate; margin rather roughly crenulated by the major ribs, more finely so by the interstitials. Color of exterior yellowish gray, the areas between the ribs splotched with blackish brown; interior delicately opalescent, with the dark rays showing through outside the usually brown-stained visceral area. Long, of holotype 11.5, lat. 8.6, alt. 5.3 mm.

Type-Locality: Punta Cholla, W. of Puerto Penasco, Sonora; S. S. Berry, 23-24 Mar. 1948, et seq.

Commentary: This small acmaeid is perhaps most similar to A. mitella Menke, and has frequently been so identified. It differs from that species in its generally larger size, lighter shell, less crowded ribs, and lack of the sharp black radial lineation so characteristic of the older species.