PLATE II. 



Unio nasutus. 

 Page oi. 

 Fig. 1. Left valve of a female, showing plications of the shell produced by- 

 growth over the gills while distended with fry. Natural size. 



Canal, West Troy, N. Y. 



Unio complanatus. 



Page 55. 

 Fig. 2. A specimen presenting characters similar to the preceding, but show- 

 ing two or more successive periods of impregnation. The 

 general form of the shell is normal and may serve for com- 

 parison with the three following illustrations of unusual exam- 

 ples. Canal, West Troy, N. Y. 



Fig. 3. A right valve having the umbo nearly central and with a strong sulcus 

 on the anterior portion of the valve. 



Canal, West Troy, N. Y. 

 Fig. 4. A very elongate cylindrical form. 

 Fig. 5. Id. Posterior view, showing the convexity of the valves. 



Hudson river, Albany, N. Y. 

 Fig. 6. A wide, regularly elliptical specimen with large, prominent, rounded 

 umbo which is situated just anterior to the middle of the 

 cardinal line. Natural size. Canal, West Troy, iV". Y. 



