CHAPTER VIII: THE BASKET CLAMS 



Family CoRBULiDiE 



Genus CORBULA, Brug. 



Shell small, thick, gaping in front, valves unequal, hinge 

 formed by a recurved tooth fitting into a socket; animal unsym- 

 metrical; mantle closed, except for the pedal aperture in front, 

 with toothed edges ; siphons united, short, fringed. An interesting 

 group of small bivalves living in sand or mud. 



The Contracted Basket Clam {C. contractu. Say) has its 

 unequal swollen valves presenting an almost circular outline when 

 seen end on, and drawn out to a truncated point at the posterior 

 end. The surface bears regular small concentric ridges. Length, 

 J inch. 



Habitat. — Cape Cod to West Indies. 



C. nasuta, Say, is more nearly equivalve, pointed more 

 sharply at the posterior end, but more nearly circular in the 

 outline of each valve. Ridges fine and close. Length, J inch. 



Habitat. — Cape Hatteras to Haiti. 



The Yellow Basket Clam (C. luteola, Cpr.) is shaped like 

 the familiar little Donax. Its yellow shell shows faint lines of 

 growth; the edges are thickened and turned inward. Length, 

 f inch. 



Habitat. — Southern California. 



The British Basket Clam (C. gibba, Olivi.) is swollen so 

 out of symmetry that the right valve contains the body, and the 

 left is like an operculum. The extended shell forms a protective 

 roof for the siphons. The foot is tongue-like. 



Cryptomya Californica, Conr., has thin, whitish, elliptical 

 unequal shell, faintly checked with crossing striations, gaping 

 behind; a peg and socket hinge; internal ligaments; the short 

 siphons not covered with tough skin. Length, i inch. 



Habitat. — California. 



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