CALYPTRACEA. MOLLUSCA. CREPIDULA. 161 



CREPfDULA GLAUCA. 



Shell oval, smooth, apex separate, slightly turned to one side ; 

 diaphragm less than half the length of the shell, edge waved. 



FIGURE 14. 

 State Coll., No. 121. Soc. Cab., No. 818. 



Crepidula glauca, SAY ; Journ. Acad. Nat. Sc., ii. 226. 



Shell obliquely oval, thin, moderately convex, of a glaucous or 

 grayish-green color, faintly freckled with dots of darker and 

 lighter color ; surface nearly smooth ; the apex is pointed, pro- 

 jecting considerably beyond the outline of the aperture, and, turn- 

 ing downwards, and a little to one side, does not quite reach the 

 plane of the aperture ; aperture rounded oval, the margin usually 

 expanded ; interior a uniform, dark reddish-brown, or occasionally 

 mottled ; the edge is margined with yellowish-white, and dotted 

 with brown ; diaphragm white, running within the beak so as to 

 exhibit a considerable recess ; it is waved, two thirds being con- 

 vex, and the remainder concave ; the free margin has a concave 

 curve in proportion as the diaphragm is arched. Length { inch, 

 breadth ^ inch, height y 1 ^ inch. 



I have taken only one specimen of this shell, which I found 

 on a stone dragged upon Chelsea Beach by a Laminaria attached 

 to it. It is, however, common on the ocean shore of Rhode 

 Island, and is doubtless to be found at the Elizabeth Islands, and 

 along the South Shore. The specimens I have received from 

 Colonel Totten have a peculiar figure, and from their undulated 

 edges I should conjecture they were taken from off the Pecten 

 concentricus, which is found abundantly about Cape Cod. 



It is readily distinguished from C. convexa by its depressed and 

 broader figure, and white diaphragm. From small specimens of 

 C. fornicdta it is distinguished by its projecting and central apex, and 

 by the constant recess under the beak. In some specimens the arch- 

 ing of the diaphragm is greater than in others, and then its free mar- 

 gin is more or less curved also. There is no decided notch at either 

 extremity. 



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