86 GASTROCH^NID.E. 



Cieiins MONTACUTA, Turton. 1819. 



Shell ovate or oblong, G(]uivalvc, inequilateral, nearly closed ; 

 hinge with two teeth in each valve, and a cavity between them ; lat- 

 eral teeth none. 



Montacuta elevata. 



Shell ovate, trian!:]cular, Ijcalc^ tumid, elevated, nearly central, disk flattened 

 below the middle ; tooth on the shorter side oblique, and excavated for the recep- 

 tion of the ligament. 



Montacuta hidentata, Gould, Inv. Mass. 1st cd. .59 (non auct ). 

 Montacuta elevata, Stimpsox, IShells of New Eiij^laml, 16 (18.51). 



Shell minute, fragile, white within and without, or with a very 

 thin straw-colored epidermis, ovate-triangular; beaks nearly central, 

 nearest the broader end, acute and prominent, inclined inwards and 

 slightly forwards ; uj)i)cr margins sloi)ing rajjidly from the 

 beaks in a gentle curve ; both ends obtusely rounded ; sur- 

 face shining, but rendered somewhat scabrous or rough l)y 

 numerous loosely cohering edges of the stages of growtli ; 

 its only variation in color consisting in the opacity or 

 trans})arency of its substance ; very tumid, but the disk 

 is compressed below so as to make the shell more or less 

 wedge-like. Within |)olished, destitute of any apparent muscular or 

 pallial ini])ressions, except in very old specimens, l)ut faintly marked 

 with radiating lines. Hinge consisting of two teeth, diverging from 

 the beaks, so as to leave a triangular vacancy between them ; one 

 of them considerahly elevated, and more so in one valve than in the 

 other ; that on the shorter slope scarcely rises at its tip above the 

 edge of the valve, and its inner surface is excavated, and receives 

 the ligament. Length, nearly one fifth of an inch ; height, one sixth 

 of an inch; breadth, one tenth of an inch. 



Found by Mr, C. F. Shiverick in New Bedford Harlior ; King's 

 Beach, Swampscott {Haskell) ; Chelsea Beach, thrown up alive 

 (^Stinipson). 



Family GASTROCHyENIDyE. 



Shell equivalve, generally gajnng, hinge very sim])le, often en- 

 closed in a tulie ; animal clulj-shaped, siphons very long, united to 

 near tips ; mantle closed, except for a worm-like foot ; generally 

 borers. 



