EXPLANATION OF PLATE XXIIL 



Fig's 73 A and B. — Lastena suhorhiculata (Say) 9 , Lower Lake Contrary, 

 St. Joseph. 



Fig's 73 C — F. — Juveniles of L. si(borbiculata. — Upper L. Contrary — 

 Note the coarse Anodontine beak sculpture which reaches well down on the 

 disk. 



Fig's 74 A and B. — Lastena ohiensis Raf.O, Singleton Lake, Halls. 



Fig's 75 A and B. — Anodonta grandis (Say) 9, Mud Lake, Kenmoor. 



