766 PILEUROBEMA 
terior ridge rounded, ending behind near the base in a rounded 
point; surface irregularly, concentrically striate; epidermis 
tawny or tawny-brown; pseudocardinals triangular, two in the 
left valve and three in the right; laterals two in the left valve 
and a double one in the right; beak cavities shallow; muscle 
scars small and impressed; nacre silvery-white, iridescent he- 
hind. 
Length 35, height vertically from the beaks 38, from beak: 
to post-basal point 43 mm. 
Alabama River system; Flint River, Georgia. 
Type locality, Elk and Flint Rivers, Ala. 
Unio mytilloides Conrap, Am. Jl. Sci., XXV, 1834, p. 343, pl- 
1, HIS 7 
Unio cor Conran, New F. W. Shells 1834, p. 28, pl. 111, fig. 3. 
—CneENu, Bib. Conch., 1st ser., JI], 1845, p. 16, pl. 11, fig: 
2. 
Margarita (Unio) cor Lma, Syn., 1836, p. 21; 1838, p. 18. 
Margaron (Unio) cor Lua, Syn., 1852, p. 26; 1870, p. 39. 
Pleurobema cor SIMPSON, Syn., 1900, p. 754. 
Unio crapulus Lua, Pr. Ac. N. Sci. Phila., V, 1861, p. 39; Jl. 
Ac. N..Sci. Phila: V1.W1866, ‘p..42, pi xvachs: 40: Obs ae 
1867, p. 46, pl. xv, fig. 40. 
Margaron (Unio) crapulus Lea, Syn., 1870, p. 41. 
Umolewisu les, Pr. Ac; N. Sei. Phila, V5 1861, p: 40: Ave 
N;.sci Phila.y V5 1862, p:.75,.pl> want, tic 220 Obs, Wine 
1862, p. 75, pl. Vull, 1ig220: 
Margaron (Unio) lewisti LEA, Syn., 1870, p. 56. 
Conrad’s shell is evidently fully adult or old; Lea’s U. lewis 
and crapulus are young or barely adult specimens of what 
seem to me to be the same. The species is less angular than 
P. taitanum, and the disk is evenly swollen, there being no 
compression in front of the posterior ridge. 
Conrad says this is between Unio ellipsis Lea and mytiloides 
Rafinesque, but that he has no doubt that it is the latter. It 
is certainly very different from the shell Rafinesque figures 
and describes as Pleurobema mytiloides. (Am. Gen. Sci. 
Phys. Brux., XII; 1820, p. 313) pl. 1x%x11,; fies, 6-10). iCan- 
