Diodora saturnalis (Carpenter, 1864). Distinguished from D. inaequalis by being thicker-shelled, broader, and higher for the length: marginal crenula tions are coarser. The orifice is about one-third the distance back from the anterior margin, small, slotlike, three-lobed, rounded in older specimens. The margin is nearly in one plane, or only slightly arched upward at the sides. The callus is bordered with gray, as in D. inaequalis. Length, 24 mm; width, 17 mm; height, 10 mm. Carpenter chose the name because the "hole resembles the telescopic appearance of Saturn when the rings are reduced to a line." San Ignacio Lagoon, Baja California, throughout the Gulf of California and south to Salinas and the Galápagos Islands, Ecuador.