TBS see EP ore ED ee 
Mr. Barnes on the Genera Unio and Alasmodonta. 125 
gin, straight with the beaks projecting aboveit; anterior dorsal 
margin rounded 3 anterior margin emargin nate ; anterior ba- 
sal margin; compressed and a little shortened, basal an 
posterior margins roun ndec A __Epidermis horn color, Surface 
irregular] 
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. Lateral teeth short, thick, rough, crenated and 
terminating abruptly at both ends. Cavity deep and angu- 
lar admitting the end of the fore finger. 
marks. —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 strie on the anterior lunule, © 
giving to that part, a feather-shaped appearance. Other 
cimens have the lunule wrinkled and granulated. This 
shell will stand on the posterior side though not quite ee 
but leaning towards the hinge. 
8. Unio Tuberculatus. Fig. 8. 
Shell, long-ovate, surface corr ugated, waved tuberculated, 
ribbed. Disks pconmasenans base falcated. 
. Ouisconsin, Prof. Douglass. . 
Cabinets of Lyceum and Dr. Mitchill. 
rey | Length, ae Breadth, be 
13 
13 a 6: 
Shell thick and rugged 3 anterior side compressed, nar- 
towed thin; posterio or siden rounded, short, obtuse, and 
broader than the interiour. Beaks flat, placed about two 
ninths from the posterior end; ligament higher than the 
eaks ; hinge-margin nearly s 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 !ongitudinally ; those near the base 
larger; an elevated ridge extending from the beaks and 
