40 University of Michigan 
Alasmidonta varicosa (Lam.), Simpson, ’o1, p. 17 (Atlantic drain- 
age). 
Alasmidonto (Rugifera) varicosa (lam.), Simpson, ’14, p. 506. 
Alasmidonta (Decurambis) 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 (“wndati’”) ; 
the other Alasmidonta undulata (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, pl. 3, f. 5. 
Anodonta pennsylvanica Yamarck, “19, p. 86 (Schuylkill River, 
Phila.). 
Anodonta undulata Say = A. rugosus Sw., Conrad, ’34, p. 73; Ferus- 
SAG 35s De 25: 
Strophitus undulatus (Say), Simpson, 14, p. 349. 
STROPHITUS RUGOSUS (Swainson), 1822 
Type locality: United States. 
Anodon rugosus Swainson, ’22, pl. 96. i : 
Strophitus edentulus (Say), '29—= Anodon rugosus Sw., Simpson, 
"14, DP. 345. 
Strophitus edentulus (Say), Walker, 18¢, p. 176. 
The two forms are distinguishable, but have been misunder- 
