80 



rounded; posterior margin wide, direct; basal margin 

 straight, parallel with the ligament margin; summits 

 rather prominent; disks smooth, with a few very 

 small tubercles on the posterior side; epidermis olive- 

 yellow, very broadly rayed with green; within white. 



SYNONYMES. 



U. prasinus, Nob. New Fresh Water Shells, p. 44. May, 1834. 

 U. schoolcraftensis, Lea. Trans. Amer. Phil. Soc., new series, 



vol. iv. p. 149, pi. iii. fig. 9. Sept. 1834. 

 Cab. A.N. S.No. 1128. 



OBSERVATIONS. 



Inhabits the Scioto river, Indiana. 



The specimen of this shell in the cabinet of the 

 Academy of Natural Sciences was brought by Mr. 

 Schoolcraft from Fox river, of Green Bay — others 

 are in the collection of Mr. Hyde. The species differs 

 from U. bullatus, Raf., in being of a suborbicular out- 

 line, more compressed, with much less prominent 

 beaks and fewer tubercles. Some specimens have a 

 few rather large tubercles near the base. 



UNIO NODULATUS. 



Plate XLV.— Fig. 1. 



DESCRIPTION. 



Shell suborbicular, slightly ventricose, moderately 

 thick; posterior margin direct, retuse in the middle; 

 ligament margin straight, elevated, scarcely declining; 

 disks with two series of distant prominent tubercles; 



