274 CALYPTRiEIDiE. 



nearly upright, while the other is sloping ; but sometimes the two 

 sides are nearly similar. The diaphragm is regularly arched, the 

 arch terminating at a regularly curved, depressed line, on one side, 

 and here the free edge makes a slight projection. 



This shell is easily distinguished from all our other species by its 

 convexity and l)y the color of its deeply seated diaphragm. 



[Animal l)lack, except bottom of foot, which is gray of various 

 shades, edged with dark ; tentacles white, edged with Ijlack ; lobes 

 of mantle white ; tentacles short, blunt, but capable of elongation 

 and tapering ; eyes black, on the exterior sides of the tentacles, 

 near their bases. 



Crepidula glauca, 



Tig. 14. 



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

 than half the length of the shell, edge waved. 



Crepidula glauca, Say, Journ. Acad. Nat. Sc. ii. 226 (1822) ; cd. Binney, 72. — Gould, 

 Inv. Isted. 151, fig. 14. -De Kay, N. Y. Moll. 159. 



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, project- 

 '^' ' ' ing considerably lieyond the outline of the aperture, and, 

 turning 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 

 L.. giauca. YQ(]^^{^\\-hvow\\, ov occasioually mottled ; the edge is mar- 

 gined with yellowish-white, and dotted with brown ; diaphragm 

 white, running within the lieak so as to exhibit a considerable re- 

 cess ; it is waved, two thirds being convex, and the remainder con- 

 cave ; the free margin has a concave curve in proportion as the dia- 

 phragm is arched. Length, eleven twentieths of an inch; breadth, 

 nine twentieths of an inch; height, one tenth of an inch. 



I have taken only one specimen of this shell, wdiich 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 conjec- 

 ture they were taken from off the Pecten irradians, which is found 

 abundantly about Cape Cod. 



