170 American Seashells 



Crucibulum spinosum Sowerby Spiny Cup-and-saucer 



Figure yi 



Southern California to Chili. 



% to I inch in diameter, variable in height ( % to % as high), and usually 

 with an almost circular base. Exterior with a smoothish apical area, the re- 

 mainder of the shell with radial rows of small prickles or sometimes erect, 

 tubular spines. Interior glossy, chestnut-brown, sometimes with light radial 

 rays, and with a delicate white cup attached by one side. A very common 

 species from low water to 15 fathoms. Albino shells are sometimes found. 



Subgenus Dispotaea Say 1826 

 Crucibulum striatum Say Striate Cup-and-saucer 



Plate 2ir 



Nova Scotia to South Carolina (and Florida?). 



I inch in diameter, cap-shaped, base round, edge smoothish and the 

 slightly twisted apex near the center of the shell. Interior of shell with a 

 small, shelly cup, of which only 73 is free from attachment to the main 

 shell. Apex wax color and smooth; remainder of exterior with small, wavy, 

 radial cords. Interior glossy, yellow-white or tinted with light orange-brown. 

 Commonly dredged in shallow water. 



Genus Crepipatella Lesson 1830 

 Crepipatella lingiilata Gould Pacific Half-slipper Shell 



Plate 20k 



Bering Sea to Panama. 



H to % inch in diameter, thin, almost circular, low and with the apex 

 near the edge of the shell. Characterized by its tannish to mauve-white, 

 glossy interior which has a shallow deck which is attached to the main 

 part of the shell only along one side. The middle of the deck often has a 

 weakly raised ridge. Exterior wrinkled and brownish. A very common 

 species found on rocks and on the shells of living gastropods. 



Genus Crepidula Lamarck 1799 



Crepidula fornicata Linne Common Atlantic Slipper-shell 



Plate 2im 

 Canada to Florida and to Texas. 



% to 2 inches in size. Shelly deck extending over the posterior half on 

 the inside of the shell. The deck is usually concave and white to buff. Its 

 edge is strongly sinuate or waved in two places. Exterior dirty-white to 

 tan, sometimes with brownish blotches and rarely with long color lines. 



