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Rh dull white with a thin yellowish periostracum. A4oderately common from 6 to I GO fathoms. Corbiila luteola Carpenter Common Western Corbula Monterey, California, to Panama. % inch in length, slightly obese, with the right valve more obese and overlapping the left valve on the ventral margin. Anterior end elliptical in outhne; posterior end coming to a blunt point. Beaks strong, close to- gether and slightly nearer the posterior end. Shell porcellaneous, whitish gray and may be flushed with pinkish or purplish. Interior whitish, but commonly yellowish with purple-red staining. Sculpture of weak, concen- tric crrowth lines which are less noticeable toward the smoothish beaks. Common in some localities in sand and rocky, rubbly beaches to 25 fathoms. C. rosea Williamson is merely a pink color phase of this species. Corbula porcella Dall Ribbed Western Corbula Santa Rosa Island, California, to Panama. V4 to Ys inch in length, similar to luteola, but much fatter, chalky, gray, and with much stronger concentric riblets. The right valve overlaps the left valve very prominently on the ventral margin. Moderately common from shallow water to 53 fathoms. Fa7nily GASTROCHAENIDAE Genus ROCELLARIA Blainville 1828 Both valves fairly thin, somewhat chalky in substance, and equal in size and shape. The anterior gape is very large. Beaks very near the anterior end. Hinge-teeth obscure. These clams form flask-shaped excavations in the rocks which they line with calcareous material. When not protected by a burrow, they form a shelly tube to which debris is attached. Gastrochaena Spengler is another genus from the Indo-Pacific area (formerly Fistula7ia Brug., not Miiller). Rocellaria hians Gmelin Atlantic Rocellaria North Carolina to Texas and the West Indies. % to % inch in length; valves rather spathate, with low, indistinct, fine, concentric ridges. Posterior end large and rounded. The entire anterior- ventral end is widely open to accommodate the foot. Color white. Common