Leda (Adrana) penascoensis, new species
Punta Pefiasco, Sonora, dredged 10 fathoms (1934). Type 11393, Lowe collection.
Shell white, with a straw-colored glossy periostracum; strongly compressed beaks much nearer the anterior end. Dorsal line nearly straight, ventral margin curved, anterior and posterior ends about equally angular. Dorsal edges of both valves slightly crenate the entire length. Sculpture of fine concentric lines of growth over the entire surface of both valves, except a narrow portion bordering the posterior dorsal margin, which is entirely smooth. Diameter 37.5 mm., altitude 9.4 mm. This shell differs considerably in sculpture and shape from the three other forms described in this group from West America.