160 INVERTEBRATA OF MASSACHUSETTS. 



Linnseus is distinguished by a profound notch at one extremity of the 

 partition, and a feebler one at the other ; that the shell described by 

 Mr. Say as Crepidula plana wants this notch, and is the shell figured 

 by Broderip. Now it so happens, that the only specimen which I am 

 certain is entire has this notch precisely as described, and the tooth- 

 like process which separates the large notch from the rest of the mar- 

 gin is such as would be likely to be broken in almost every instance. 

 This fact leads me to suppose, that all three of the shells in question 

 are of the same species, and should be called C. unguiformis. If so, 

 its habitat is as wide as that of C. fornicata. But as I have not yet 

 the means of confirming my supposition, I give Mr. Say's name. 



CREpfDULA CONVEXA. 



Shell elevated, apex terminal, separated from the body of the 

 shell ; diaphragm convex, less than half the aperture, edge simple. 



FIGURE 15. 



State Coll., No. 122. Soc. Cab., No. 822. 



Crepidula convexa, SAY ; Journ. Acad. Nat. Sc., ii. 227. 



Shell small, opaque, very convex, obliquely ovate, one side 

 nearly vertical, the other sloping ; surface wrinkled, color ashen- 

 brown, with bands, stripes, or dots of dark reddish-brown ; apex 

 acute, separate from the body of the shell, turning very little to 

 one side, and downwards as far as the tip of the shell ; within 

 shining, of a uniform dark reddish-brown color ; aperture oval ; 

 diaphragm deeply situated, leaving a cavity extending into the 

 beak, convex, brown, the free edge white and simply curved. 

 Length ^ inch, breadth --$ inch, height -^ inch. 



Found on sea-weed, and on stones among the roots of sea-weed. 



It is seldom found entire. Mr. Say described from dead shells, and 

 had not seen its true colors. In most instances one side is nearly 

 upright, while the other is sloping ; but sometimes the two sides are 

 nearly similar. The diaphragm is regularly arched, the arch termi- 

 nating 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 by the color of its deeply seated diaphragm. 



