Occasional Papers of the Musewm of Zoology 7 
“Conrad gave an excellent description of U. cor. His figure 
is poor, representing the shell as too full in the beaks and too 
convex. It is a case of emphasizing, or in this case of ‘restor- 
ing,’ a prominent feature, such as may be found in many pub- 
lished figures. The figure, like others in the same paper, was 
reduced, therefore drawn free-hand, and it has the faults of 
many of Conrad’s free-hand figures. 
“Writing in 1834, Conrad could not be expected to so 
describe his species as to exclude others, yet to be discovered, 
in a numerous and difficult group. 
“The type form of U. cor has apparently not been redis- 
covered. It has the beaks more produced than U. edgarianus, 
is thicker, more solid, the valves less broadly impressed, the 
epidermis less polished. As species go in this group, it would 
be considered distinct from edgarianus. 
“P. appressa Lea has more the texture of cor, but it has a 
less angular posterior ridge and is invariably more com- 
pressed. ‘This is particularly noticeable if small specimens of 
appressa of the size of cor are compared. The somewhat 
ebenus-like beaks of cor are another distinguishing feature. 
“P. cor is thus distinct from edgariana and appressa as spe- 
cies are now estimated in that group of Pleurobemas.” (H. 
iN, oI.) 
The localities given by Conrad for this species are the Elk 
and Flint rivers, Alabama, both of which are in the Tennessee 
system. 
MEGALONAIAS GIGANTEA (Barnes), 1823 
Type locality: Mississippi River, Prairie du Chien. 
Unio giganteus Barnes, ‘23, p. 119 (as variety of U. crassus Say). 
Unio undulatus Barnes, ’23, p. 120, pl. 2, f. 2. 
Unio heros Say, ’29, p. 201. 
U. undulatus Bar.=U. heros Say, ’31, pl. 16. 
