40 University of Michigan 



Alasmidonta varicosa (Lam.), Simpson, 'oi, p. 17 (Atlantic drain- 

 age). 



Alasmidonto (Rugifera) varicosa (Lam.), Simpson, '14, p. 506. 

 Alasmidonta (Decuranvliis) varicosa (Lam.), Ortmann, '19, p. 190. 



The description of U. varicosa from Schuylkill River, "U. 

 testa ovato-rhombea, tenui, fusco^ virente, radiata; natibus 

 rugis crassis, undatis, variciformibus," fits best the species of 

 the marginata group of the Atlantic drainage. Two other 

 species with "variciform" beak sculpture come into question — 

 first Strophitus edentulus (Say), but of this the bars of the 

 beak sculpture are not very heavy and not waved ("tmdati") ; 

 the other Alasmidonta imdidata (Say), with very heavy beak 

 sculpture, has not a "thin" shell. Thus, varicosa is identifiable, 

 and, in addition, this identification has been confirmed by Lea, 

 by the examination of the type, in so far as he pronounced it 

 to be marginata — that is to say, the Atlantic representative of 

 the western marginata. This determination was made before 

 any other name was given to this form. Thus, varicosa is 

 valid also on this ground. 



Strophitus undulatus (Say), 1817 

 Type locality: Not given (probably near Philadelphia). 



Anodonta undulata Say, '17, pi. 3, f. 5. 



Anodonta pennsylvanica Lamarck, '19, p. 86 (Schuylkill River, 

 Phila.). 



Anodonta undulata Say = A. rugosus Sw., Conrad, '34, p. 72 ; Ferus- 

 sac, '35, p. 25. 



Strophitus undulatus (Say), Simpson, '14, p. 349. 



Strophitus rugosus (Swainson), 1822 



Type locality: United States. 



Anodon rugosus Swainson, '22, pi. 96. > 



Strophitus edentulus (Say), '29= Anodon rugosus Sw., Simpson, 



'14, P- 345. ^ 



Strophitus edentulus (Say), Walker, '18^, p. 176. 



The two forms are distinguishable, but have been misunder- 



