26 University of Michigan 
U. triangularis Raf. =U. lateralis Raf. =U. sintoxia Raf.—= U. 
pachostea Raf.=U. mytiloides Raf.=U. rubra Raf.= U. pyramida- 
tus Lea, Conrad, ’34, p. 72. 
U. scalenius Raf. =U. cuneata Raf. =U: patulus Lea, Conrad, 34, 
p71. 
U. cuneatus Raf. = patulus Lea, Ferussac, °35, p. 28. 
U. mytiloides Raf.=U. pyramidatus Lea=U. rubra Raf., Ferus- 
sac, “35, p: 28. 
U. clava Lam.=U. scalenia Raf., Ferussac, *35, p. 28. 
U. clava Lam.=U. scalenws Raf., Conrad, ’35, p. 5, pl. 3, £. 1; 
Lea, °38, p. 126. 
U. mytiloides Raf. =U. rubra Raf. =U. pyramidatus Lea, Conrad, 
"30; ‘p:- AT, pl.22p. 
Cunicula patula (Lea), Swainson, ’40, p. 378. 
Pleurobema clava (Lam. ) and Pl. mytiloides (Raf.), Agassiz, ’52, 
p. 49. 
Pleurobema clava (Lam.), Simpson, ’00°, p. 745; 14, p. 735. 
Pleurobema clava (Lam.) =U. elliptica Raf.= Obl. scalenia Raf, 
= Pl. cuneata Raf., Vanatta, ‘15, p. 555 (‘‘types” examined). 
The original description of U. clava Lam. is very poor ; how- 
ever, a “sublongitudinal, oviform shell, with the anterior (pos- 
terior) side very short,” cannot be referred to any other Amer- 
ican species. The short anterior side (indicating the anterior 
position of beaks) is very characteristic. This identification 
is confirmed by Lea’s examination of the type. The original 
locality (Lake Erie), given by Lamarck, is erroneous. 
Pl. mytiloides Raf. has been taken by Conrad and others to 
be U. pyramidatus, but it is clearly recognizable from Rafin- 
esque’s description and figure. The latter, as usual, is exag- 
gerated, but distinctly represents a phase frequently assumed 
by clava, chiefly when old. It cannot be pyramidatus on 
account of the presence of distinct rays. The recognition of 
mytiloides has no bearing upon the nomenclature of the spe- 
cies; it is, however, important for that of the genus (see 
above). 
The identification of scalenia Raf. with this species is evi- 
dent from the original description and figure and is confirmed 
