Page:American Seashells (1954).djvu/549

Rh

Figure 91. Rangia Marsh Clams of the Atlantic Gulf States, a and b, Rangia cnneata Gray, 2 inches; c and d, R. flexiiosa Conrad, i % inches. distinct pallial sinus, with much shorter laterals, with a faintly impressed, large lunule, and colored light-brown inside. A rare and elusive species from marsh areas. R. rostrata Petit is a synonym. Family MESODESMATIDAE Genus Mesodesma Deshayes 1830 Like a large Donax with a prominent chondrophore. fine denticles. Laterals with Mesodesma arctatimt Conrad Greenland to Chesapeake Bay. Arctic Wedge Clam Plate 32r About I 'V2 inches in length, somewhat shaped like a Donax, fairly thick and compressed. Chondrophore fairly large and spoon-shaped. Left valve with a long anterior and posterior lateral tooth, both of which have fine, comb-like teeth on each side. Pallial sinus small and U-shaped. Interior tan to cream. Exterior with a thin, yellowish, smooth periostracum. Common from low water to 50 fathoms.