Occasional Papers of the Museum of Zoology 21 
either ground in giving clava Lam. as the type of Pleurobema, 
because mytiloides is a synonym of clava. 
The designation of U. scalenius Raf. as the type of Scale- 
naria by Herrmannsen makes this name a synonym of Pleuro- 
bema (we choosing to give preference to the latter according 
to Art. 23 of the Code, concerning names of the same date), 
and renders the subsequent designation of another species by 
Agassiz as the type of Scalenaria wholly inoperative. 
PLEUROBEMA CORDATUM (Rafinesque), 1820 
Type locality: Ohio River. 
Unio obliqua Lamarck, ’19, p. 72. 
Obliquaria lateralis Rafinesque, ’20, p. 310. 
Obovaria cordata Rafinesque, ’20, p. 312, pl. 82, figs. 6-7. 
U. obliqua Lam.=U. undatus Bar. (23), Lea, ’34, p. 28 (type 
examined). 
U. cordatus Raf.=U. obovata Raf. (for obovalis ?), Conrad, 734, 
p. 68. 
U. triangularis Raf. = lateralis Raf. = sintoxia Raf. = pachostea Raf. 
= mytiloides Raf. =rubra Raf.= pyramidatus Lea, Conrad, 734, p. 72. 
U. obliqua Lam. = obovalis Raf. = ebenus Wea, Ferussac, ’35, p. 28. 
U. cordatus (Raf.) Conrad, ’36,. p. 48, pl. 25. 
U. obliauus Lam. =undatus Bar. = cordatus Con., Lea, ’38, p. 125. 
U. obliquus Lam. and U. solidus Lea, Call, ‘oo, pp. 501, 504, pl. 57, 59. 
Quadrula obliqua (Lam.), Simpson, ’14, p. 88r. 
Quadrula obliqua Lam. = Obliq. lateralis Raf., Vanatta, ’15, p. 557 
(“type” examined). 
Quadrula cordata Raf. =Q. plena (Lea), Vanatta, ’15, p. 558 (“type” 
examined). 
Quadrula obliqua Lam. = oblig. lateralis Raf., Walker, ’18°, p. 167 
(fide Vanatta). 
That the description of U. obliqua Lam. is imperfect and 
that the species cannot be identified from it has been stated 
by Lea (’29, p. 422). Later (’34) he identified obliqua from 
the type as undatus Bar., which, as we see from his Synopsis 
in 1838, is the same as cordatus Con. (’36), while the real 
undatus is a Fusconaia and the same as trigonus Lea. See 
Fusconaia undata. 
