46 



Unio vcrrucoNUK, Baunes. Shell rather quadrate; 

 thick ; nuinerous loarts on its exterior. Color within, 

 bluish-slate. Vermillion and Illinois rivers. 



I'nio xift-zas. Lea. A small shell, with numerous 

 zigzag liiu^s and blotches of a green color. Bluish- 

 white within. I can see no difference between this 

 species and U. donaciformis. Lea. Loc. Illinois river. 



SUBGENUS MARGARITANA, Schum. 



This biH)^d, flat species is abundant in the Illinois 

 river. 



j«AltC»AKI TA-^'A RlJCiiOSA, Baknes. 



This well-marked shell is abundant in the Fox, Illi- 

 nois, and Vermillion rivers. 



HAK<.JAniTA-'VA CO.^FK ACJOSA, Say. 



This shell is sufficiently marked by its peculiar 

 broken undulations and the knotty appearance of the 

 beaks, to distinguish it from any other species. 



IWARtJARITA.^A I>KI/1 OII>EA, Lea. 



This small deltoid species inhabits the Illinois river. 



Iflargaritana marjarinata. Say. Shell OVate, thin, 



wedge-shaped from before ; beaks small but elevated, 

 with several undulations. Color, olive green, mottled 

 with broken lines of a darker color. Within, bluish. 



