43 INVERTEBRATA OF MASSACHUSETTS. 



FIGURE 28. 

 State Coll., No. 231. Soc. Cab., No. 2322. 



Anatina papyratia, SAY ; Journ. AcaA. J\Tat. Sc., ii. 314. 

 Anatina papyratia? TOTTEN ; Siilimari's Journ., xxviii. 347, f. 1. 



Shell small, broadly rounded-ovate, fragile and thin, white and 

 pearly ; the right valve most convex ; inequilateral, the posterior 

 or shorter side narrowed, and at the tip clipped, and moderately 

 gaping ; margin, from the beak backward, a-straight line ; the rest 

 of the outline regularly curved ; beaks placed about one third of the 

 length of the shell from the posterior extremity, moderately prom- 

 inent, inclining forwards, and cleft across the middle ; from the 

 beaks to the lower posterior angle runs an elevated, angular ridge ; 

 surface finely marked by the lines of growth, vestiges of a yellow- 

 ish-white epidermis ; interior pearly ; tooth long and narrow, 

 slightly concave, directed obliquely across the shell, supported 

 beneath by a short, sharp, elevated rib ; muscular and palleal im- 

 pressions very superficial. Ossiculum somewhat like two cres- 

 cents joined at the extremities, fitting in front of the teeth. 

 Length -i-| inch, height J inch, breadth J inch. 



Found in the stomachs of fishes caught off Nahant ; and taken 

 by dredging in Newport harbour by Colonel Totten. 



This is undoubtedly the shell described at length by Colonel Totten, 

 and for which he proposes the specific name frdgilis, provided it be 

 not the A. papyratia of Say. Mr. Say's dimensions differ a little in 

 their proportions from the New England shell; but our shells have 

 sufficient latitude of dimensions to render this variation of little im- 

 portance. 



The only shell we have that resembles it, is the Sanguinoldria fusca ; 

 but that shell has less breadth, is equilateral, and rounded through- 

 out, besides the great difference of the hinge. 



GENUS COCHLODESMA, COUTHOUF. 



Shell inequivalve, inequilateral, slightly gaping at both ends ; 

 beaks small, cloven ; hinge a spoon-shaped process in each valve, 

 supported by an oblique rib, and receiving the cartilage. 



