PL_EUROBEMA 767 
rad’s Unio cor was published in May, 1834, and his mytilloides 
in January of the same year, so that the latter has priority, 
but as Rafinesque’s name was placed under the genus Pleuro- 
bema, and as I place Conrad’s species, which is an entirely 
different thing, in the same genus, the name mytilloides can 
not be used for it, and it must therefore take the next name 
proposed, which is Conrad's cor. 
Dr. Lea admits Rafinesque’s mytiloides with doubt, and in 
his collection places under that name specimens which I regard 
as a rather elongated Quadrula pyramidata.  Rafinesque’s 
figure represents an elongated shell, almost absolutely straight 
on the dorsal line, and with the beaks carried far in front of 
the rest of the shell. I have never seen anything which at all 
agrees with it. 
PLEUROBEMA PEROVATUM (Conrad). 
Shell irregularly oval, inflated, rather thick, inequilateral ; 
beaks full, high and rounded, undulated, placed not very near 
the anterior end; anterior end rounded, slightly cut away be- 
low; base line curved; post-dorsal line raised into a decided 
angle at some distance behind the ligament; below this angle 
the posterior end is obliquely truncate; posterior ridge narrow- 
ly rounded; epidermis olive; pseudocardinals erect and promi- 
nent, not very thick; laterals straight, compressed; anterior 
muscle scars deep; posterior scars impressed; nacre white, 
much thinner behind. 
Length ef Conrad’s figure 44, height 30 mm. 
Tvpe locality, Prairie Creek, (tributary of the Tombigbee), 
Marengo County, Alabama. Also small streams, Greene Co., 
Ala. 
Unio perovatus Conrap, Am. Jl. of Sci, XXV, 1834, p. 338, 
pl. 1, fig. 3; ?New F. W. Shells, 1834, p. 47, pl. 1, fig. 3.— 
€Henw, Bib. Conch., rst. ser., II; 1845, p. 22, pl. 1, fig: 3. 
Margarita (Unio) perovatus IA, Syn., 1836, p. 23; 1838, p. 
10. 
Margaron (Unio) perovatus Tea, Syn., 1852, p. 27; 1870, p. 
42. 
Pleurobema perovata Simpson, Syn., 1900, p. 755. 
