86 gastrochj:nid.e. 



Oemis MONT ACUTA, Turton. 1819. 



Shell ovate or oblong, equivalve, inequilateral, nearly closed ; 

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

 eral teeth none. 



Montacuta elevata. 



Shell ovate, triangular, beaks tumid, elevated, nearly central, disk flattened 

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

 tion of the ligament. 



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

 Montacuta elevata, SxiMPSGN, iShells of New England, 16 (1851). 



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

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

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

 slightly forwards ; upper margins sloping rapidly from the 

 Fig. 393. beaks in a gentle curve ; both ends obtusely rounded ; sur- 

 face shining, Ijut rendered somewhat scabrous or rough by 

 numerous loosely cohering edges of the stages of growth ; 

 its only variation in color consisting in the opacity or 

 transparency of its substance ; very tumid, Init the disk 

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

 wedge-like. Within polished, destitute of any apparent muscular or 

 pallial impressions, except in very old specimens, but 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 considerably 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 Harbor; King's 

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

 ( Stimpsori) . 



Family GASTROCH^NID^. 



Shell equivalve, generally gaping, hinge very simjile, often en- 

 closed in a tube ; animal club-shaped, si])hons very long, imited to 

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

 borers. 



