Occasional Papers of the Museum of Zoology 27 
by the so-called Rafinesque-Poulson “type.” It has no bearing 
upon the nomenclature of this species, but is important for 
the validity of the subgenus Scalenaria (Scalenilla) of the 
genus Dysnomia (which see). 
PLEUROBEMA LEWISI (Lea), 1861 
Type locality: Coosa River, Alabama. 
Unio lewist Lea, 61, p. 40. 
Pleurobema cor Simpson, ’14, p. 765 (not U. cor Conrad, ’34). 
Pleurobema lewisi (Lea), Walker, *16*, p. 114. 
The synonymy of this species has been settled by Walker 
and nothing remains to be added. 
PLEUROBEMA SIMPSONI Vanatta, 1915 
Type locality: Chattahoochee River, Columbus, Ga. 
Unio striatus Lea, ’40, p. 287 (not U. striatus Goldfuss, ’39). 
Pleurobema striatum (1,ea), Simpson, 714, p. 795. 
Pleur. simpsoni Vanatta, *15, p. 539. 
Unio striatus Lea, Walker, ’16¢, p. 47. 
Pleurobema simpsoni Van., Walker, ’18¢, p. 173. 
The introduction of simpsoni Van. is justified (see Wal- 
ker 718o): 
However, attention should be called to the probability that 
U. modicus Lea (°57, p. 157), Pleurobema modicum Simpson 
(14, p. 794) and U. amabalis Lea (’65, p. 89) and Pleuro- 
bema amabile Simpson are synonyms of U. striatus, In this 
case either would have priority, modicus being the earlier 
name. 
Genus Erzrptio Rafinesque, 1819 
Type: Unio crassidens Lam.= U. nigra Raf. 
Elliptio Rafinesque, ’19, p. 426; ’20, p. 291 (no type named) ; Simp- 
son, ’00, 700, as section of Unio (type, U. crassidens Lam. =U. nigra 
Raf.) ; Ortmann, ’12, p. 65 (genus, type the same). 
Eurynia Rafinesque, "19, p. 426; ’20, p. 207 (no type named) ; Herr- 
