11 



C. tria "gnlarivs. Transversely oval subtriangular, subaequi- 

 lateral: 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. Inha- 

 bits M.xico. 



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

 of the calyculata, Drap., but the shell is more drawn up to an 

 angle in that part. 



ANODONTA. 



A. implicata. Transversely oblong-oval, subcylindric, yellow- 

 ish olive: disk convex, the wrinkles not very prominent; um- 

 bonial slope hardly presenting a very obtuse angle or curve: 

 beak but little elevated, obsoletely undulated: hinge margin 

 nearly parallel to the base, diverging a little from it anteriorly, 

 and terminating in a slight, obtuse angle: within deeply concave. 



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

 fifth; convexity, one inch and three-twentieths. Inhabits a 

 pond in Danvcrs, Massachusetts. 



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

 is more cylindrically convex than any I have met with. 



As respects the proportions of length and breadth, it resem- 

 bles A. elongatus, 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, exhi- 

 biting a regular curvature. 



A. 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 sinuous undulations '.^within, white: margin, particularly 

 before, livid: hinge margin, somewhat parallel to the ba 

 the sinus rather nearer the base than at the beak, or as near. 



Length, two and a half inches; breadth, four inches and 

 seven-tenths. Convexity, one inch and fou Inhabits 



Cumberland River. 



For this specimen I am indebted to Mr. Lesueur. I cannot 

 make it agree with the A. Swains., though it 



some resemblance to thai •• it is, however, a 



