138 



Oyclas transversa. — Transversely oblong subovate, sub- 

 inseqiiilateral : anterior margin decidedly more widely rounded than 

 the posterior margin : beak obviously elevated above the general 

 curvature : cardinal teeth double, distinct. 



Length, over one-fourth of an inch ; breadth, nine-twentieths of 

 an inch. Inhabits Kentucky. 



This shell is more transverse than even the simih's, nob. 



Cyclas triangularius. — Transversely oval, subtriangular, sub- 

 equilateral : disk with transverse, rather raised lines : beak some- 

 what prominent; elevated much beyond the general curvature: 

 teeth, viewed in profile, distinct and elevated. 



Length, two-fifths of an inch ; breadth, half an inch. Inhabits 

 Mexico. 



The apex of this species is not so acutely elevated as that of 

 the cali/cula(a, Drap., but the shell is more drawn up to an angle 

 in that part. 



Anodonta implicata. — Transversely oblong-oval, subcylin- 

 dric, yellowish olive : disk convex, the wrinkles not very promi- 

 nent ; urabonial slope hardly presenting a very obtuse angle or 

 curve : beak but little elevated, obsoletely undulated : hinge mar- 

 gin nearly parallel to the base, diverging a little from it anterior" 

 ly, and terminating in a slight, obtuse angle : within deeply con- 

 cave. 



Length, one inch and a half; breadth, three inches and a fifth; 

 convexity, one inch and three-twentieths. Inhabits a pond in 

 Danvers, Massachusetts. 



For this species, I am indebted to Dr. Harris, of Milton. It ia 

 more cylindrically convex than any I have met with. 



As respects the proportions of length and breadth, it resembles, 

 A. elorif/atux, Swains. ; but the umbones are less elevated and not 

 placed so far back as in that species. It is also a thinner shell, 

 and the dorsal view is altogether different, exhibiting a regular 

 curvature. 



Anodonta lugubris. — Transversely oblong-oval, subovate, 

 blackish-brown : disk convex, acutely wrinkled : umbonial slope, 

 with a distinct elevation or line : beak, slightly elevated, with 

 two or three sinnous undulations : within, white : margin, parti- 

 cularly before, livid : hinge margin somewhat parallel to the 



