Mr. Barnes on the Genera Unio and Alasmodonta. 125 



gin^ straight with the beaks projecting above it ; anterior dorsal 

 margin rounded ; anterior margin emarginate ; anterior ba- 

 sal margin; compressed and a little shortened, basal and 

 posterior margins rounded. Epidermis horn color, surtace 

 irregularly corrugated and tuberculated all over, except a small 

 portion of the posterior side. Tubercles largest near the 

 centre of the disks, and often eroded ; a strong, elevated and 

 nodulous ridge extending from the beaks to the anterior 

 margin and projecting in front. Cardinal teeth sulcated and 

 crenulated. hateral teeth short, thick, rough, crenated and 

 terminating abruptly at both ends. Cavity deep and angu- 

 lar admitting the end of the fore finger. 



Remarks. — The breadth from the emargination to the 

 posterior side is equal to the length of the shell. Two spe- 

 cimens in the Lyceum's cabinet are wrinkled regularly and 

 beautifully across the transverse striae on the anterior lunule, 

 giving to that part, a feather-shaped appearance. Other 

 specimens have the lunule wrinkled and granulated. This 

 shell will stand on the posterior side though not quite erect, 

 but leaning towards the hinge. 



8. Unio Tuberculatus. Fig. 8. 



Shell, long-ovate, surface corrugated, waved tuberculated, 

 ribbed. Disks compressed, base falcated. 



Hab. Ouisconsin, Prof. Douglass. 

 Cabinets of Lyceum and Dr. Mitchill. 

 Diam. -7 Length, 1.3 Breadth, 2-4 

 1-3 2-3 4°2 



1-3 2-4 4-5 



Shell thick and rugged ; anterior side compressed, nar- 

 rowed thin ; posterior side rounded, short, obtuse, and 

 broader than the interiour. Beaks flat, placed about two 

 ninths from the posterior end; ligament higher than the 

 beaks ; hinge-margin nearly straight, elevated, compressed 

 and carinate before; basal margin compressed, falcated; 

 anterior dorsal emarginate, anterior basal, projecting ; ante- 

 rior margin narrow and rounded. Epidermis dark brown or. 

 horn color. Surface thickly and irregularly tuberculated, 

 tubercles elongated longitudinally ; those near the base 

 larger; an elevated ridge extending from the beaks and 



