172 AMERICAN MARINE CONCHOLOGY. 



Genus MONTACUTA, Turton. 

 Conch. Diet., 103. 1819. 



1. M. ELEVATA, Stimpson. Fig. 440. 



Shells New Eag., 16. 1851. 



Montacula Mdentata, Gould (non Auct.), Invert. Mass., edit. i. 59. 1841. 



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



disk flattened below the middle; tooth on the shorter side oblique 



and excavated for the reception of the ligament. White, under a 



very thin straw-colored epidermis. 



Length 5, height 4 mill. 



New England. 



2. M. GouLDi, Thomson. Fig, 441. ^ -u /.j i .■ ,^ ,\ c<^ ■c-i-'tL/\- C^/vi/l 



Am. Journ. Cbnch., iii. 33, t. 1, f. 15. 1867. ^ 

 Shell minute, diaphanous, rhomboidal, inequilateral, not com- 

 pressed. Beaks rather prominent, not in contact, with an exca- 

 vated areola in front. Basal margin nearl}^ straight, elids obtusely 

 rounded, forming a rhomboidal outline; lines of growth regular, 

 with an opaque white thickened band surrounding the margin; 

 hinge with the cartilage occupying a pit between two rather strong- 

 teeth. 



New Bedford^ Mass. 



Genus LEPTON, Turton. 

 Brit. Bivalves, 63. 1819. 



The mantle is much produced be3'ond the margin of the shell, 

 and is furnished with slender, tentacular filaments. The foot is 

 folded as in Area, but when the animal is in motion it forms an 

 expanded disk. 



1. L. LEPiDUM, Say. Fig. 461. 



{A7np7iidesma.) Journ. Philad. Acad., v. 331. 1826. 

 Shell ver}' much compressed, subtriangular, remarkably thin, 

 pellucid, equilateral, somewhat iridescent, with numerous con- 

 centric wrinkles, and equally numerous, very minute, regular, 

 longitudinal stria?, curving towards the anterior and posterior 

 edges ; cardinal teeth obsolete, laterals prominent. 



Length G, height 6.5 mill. 



Soutli Carolina. 



2. L. LONGiPES, Stimpson. 



Bost. Proc, V. 111. 1855. 

 Shell subtriangular, somewhat rounded, slightl.y compressed, 



