76 



MACTRAD^. 



hinge margin being slightly concave, it is there somewhat nar- 

 rowed ; posterior slope convex, extremity slightly gaping, base reg- 

 nlarly cnrved ; beaks but little elevated ; before, there is a short, 

 faintly defined areola ; behind them is another portion bounded l)y 

 an elevated line extending from the beaks to near the lower an- 

 gle, and here the epidermis is very coarsely and loosely wrinkled ; 

 the surface has a rugged appearance from the coarse lines of 

 growth, and is rendered still more rugged by the folds of the 

 thick, strong, dusky-brown epidermis in the same direction. In- 





M. ovalis. 



terior bluish-white ; hinge-supports strong and smoothly rounded; V 

 tooth strong and firm, having the anterior side in the right valve 

 much more elevated than the posterior ; lateral teeth short and 

 slender, not striated ; muscular and pallial impressions rather su- 

 perficial ; sinus of the latter deep. Length, three and one half 

 inches ; height, two and one fourth inches ; breadth, one and one 

 fourth inches. 



Found at the Bank fisheries, in the stomachs of fish. Eastport 

 and Grand Manan, at low-water mark, large and plcntilul; and 

 southward to Cape Cod ( Stiuipsoii.) ; Sal)le Island (Wi//is) ; Gulf of 

 St. Lawrence (^Be/l). The young, from a fourth of an inch to an 

 inch in length, are found abundantly in fish caught in Boston Har- 

 bor. At least, they differ from the young of M. soIUUssima, and 

 correspond in external proportions and api)earance to our shell, 

 and the teeth are slender and without striae. ]\Iiddendorff gives 

 the Sea of Ochotsk, and Wossnessenski gives Behring's Straits as 



