Page:American Seashells (1954).djvu/477

Rh Lasaea cistula Keen Little Box Lepton Southern half of California to Peru. Me of an inch in length (one of the smallest of our American clams), oval-oblong to quadrate, with one end slightly more rounded. Beaks slightly- nearer the posterior end. Shell very obese to moderately inflated. Color lis^ht-tan with dark carmine around the dorsal margin area, and commonly blushed on the sides with light-carmine. Coarse, concentric growth lines, especially in the adults. Periostracum thin and yellowish tan. Found nestled together in great numbers attached to seaweed holdfasts and among mussels. Lasaea subviridis Dall (British Columbia and south) is much more com- pressed, smoother, with smaller beaks, but otherwise similar to cistula. Com- mon. Genus Pseiidopyth'ina P. Fischer 1884 Shell small and quadrangular. Lateral teeth absent; i cardinal tooth in each valve. Fseudopythina rugifera Carpenter Wrinkled Lepton Figure 80a Alaska to Lower California. % to % inch in length, oval-oblong, moderately obese, fairly fragile, beaks close together and located about the middle of the shell. Shell white, but in live specimens covered with a thin, light-brown, semi-glossy periostra- cum which is feebly and concentrically wrinkled. The ventral edge of the valves is slightly indented in the middle in some specimens. May be found attached to crustaceans and the sea mouse, Aphrodita, or be free. Vseiidopythwa compressa Dall (Alaska to Mexico, the Compressed Lep- ton) is similar in size and outline, but is considerably compressed (thinner), smoothly polished in the beak area and with much less periostracum. Com- mon. Genus My sella Angas 1877 Two cardinal teeth in the right valve, none in the left. Rochefortia Velain is this genus but a later name by several months. My sella planulata Stimpson Atlantic Flat Lepton Nova Scotia to Texas and the West Indies. % inch in length, oval-oblong in side view, well-compressed, and fairly