Mr. Barnes on the Genera Unio and Alasmodonta, 275 
Inhabits the Fox River. Mr. Schoolcraft. 
Cabinet of the ee ee 
Mr. Collins’s Collectio 
Mr. Say’s Collection, Philadelphia 
Diam. *35—-525 Length -4—-6 Breadth *75—1°2. 
Shell rather thin, beaks placed about one fourth of the 
length from the posterior extremity, ligament very narrow, 
anterior lunule distinct and obsoletely ribbed; basal margin 
slightly shortened ; epidermis brownish ; an “obtuse ‘slight- 
ly elevated rib from the beaks to the anterior basal margin; 
lateral tooth rectilinear rounded at the end, and parallel to 
the base ; ; naker very brilliant. 
Real RK.—The smallest and most beautiful of all the 
genus yet discovered in America 
| Summary of the thio: 
Species described, ants oe ae 
Varieties pérticularieed. poe = "3. = 
Total of species and varieties, ig ae ae 
Of which Mr. Say formerly Sea ete - 8 
e Sk given new specific nam 20 
Of which M. haraticr had perhaps previo no- 
a 
End of the Unio. 
ALASMODONTA.* 
Generick Character. 
Shell transverse, equivalve, i eta free; beaks 
decorticated ; posterior muscular impression compound ; 
hinge with prominent cardinal teeth in each valve, but 
witheat lateral teeth. ' 
*“<From a, without, seeue (atricue ?) a scale, and svc a tooth.”’—Mr. Say. 
