adiremneen 
Mr. Barnes on the Genera Unio and Alasmodonta. 121 
My collection. Cabinets of Lyceum and Dr, Mitchill. 
Mr. s cabinet, Philadelphia. 
75 Length, 1,0 Breadth, re mches. 
1 “ 
in age; surfac ce oR eg ieoly folded ; folds indenting 
the anterior basal edge. Cardinal teeth crtnate; sulcate ; 
rected backwards. Naker very white, tinged on the an- 
terior side with rose colour; surface polished and on the 
fore part iridescent. 
Remarks.—In young specimens the folds are visible on 
the znside, but in older ones the edge is not even indented. 
This shell very much resembles the variety (d.) of the Unio 
Crassus. Both shells will stand erect when placed on the 
posterior side, being supported by the projecting beaks. M. 
Lamarck observes that his Rariplicata is nearly allied to his 
Peruviana, but if we have not mistaken his short definitions, 
they are much more unlike than the two above mentioned. 
Our undulatus will not stand on the posterior side, as the 
beaks project very little. 
a. inside. 
4, Unio Undatus. Fig. 4 e en 
de. 
Shell, sub-triangular, sub- longi — tumid, waved ; 
lateral teeth, two in each va 
Unio Obliqua? M. Lamarck. 
Hab. Ouisconsin and Fox Rivers. Mr. Schoolcraft. 
Dr. Mitchill’s cabinet. My collection. Mr. Say’s col- 
lection. 
Length, 2:1 — Breadth, 2-2 
Shell thick, dicks swelled behind ; depressed before ; 
anterior side slightly produced, rapidly narrowed, angulated ; 
aoe Pree — mie as far as the posterior 
