Mr. Barnes on the Genera Unio and Alasmodonta. 271 
species. It most resembles the Unio Ventricosus; but is 
less, thinner, more flattened and even slightly concave on 
the anterior slope, from the oblique carina to the -angle at 
the termination of the ligament.” Mr.Say says the Ovatus is 
not rayed, and our specimens accord es his description, 
= M. Lamarck mentions a verieey with rays _— Lak ke 
eorge 
23. Unio Carrosus.—Shell ovate or var’ rife, 
not very thick, beaks somewhat prominent, cav- 
ity moderate. : 
Unio Cariosus. Mr. Sa 
Unio Cariosa. M. Lam 
Inhabits Lakes and Rivers fr N. America. 
My Collection. 
Diam. 16, Length 2-3, Breadth 3-7, 
American ‘Conchology, plate 3, fig. 
The dimensions and description of this shell vary se 
much that it is difficult to find a sufficient number of perma- 
nent characters by which it may be distinguished. It re- 
sembles in this respect the Unio Purpureus; for of the 
twélve characters mentioned by Mr. Say, and the six men- 
tioned by M. Lamarck only four can be considered as in 
any degree permanent ; and of these M. Lamarck has men- 
tioned but one, and that is “inflated.” The colour, form and 
size of the shell constantly. vary. It is commonly. broader 
before, but often equally broad at both extremities ; and 
somewhat pointed. Mt is never very thick ; often very "thin; 
commonly a medium. Those from the Hudson are thin 
and ‘genit from the Raritan thicker and broad ; from the 
western waters middle sized and of considerable thickness ; 
disks swelled, umbones elevated; ligament exterior and el- 
evated ; epidermis olive-brown or greenish, and commonly 
radiated. Internal <p bluish white, reddish, rose, or 
salmon ; surface often warty. 
‘Variety (a) Cardinal haat multipartite. 
Inhabits Lake Ontario 
Mr. Bradhurst’s Collection. 
