MESODESMATIDAE 



451 



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. 



