PLEUROBEMA 783 
what squarely truncated; base line slightly curved, outline of 
dorsal slope curved; surface irregularly, concentrically striate ; 
epidermis black, strongly, concentrically wrinkled around the 
border of the shell, nearly smooth and shining below the um- 
bonal region; pseudocardinals two in the left valve and three 
in the right; laterals straight, two in the left valve and one in 
the right; beak cavities shallow; muscle scars small; nacre 
reddish flesh-color. 
Length 50, height 30, diam. 20 mm. 
Type locality, Altamaha and Flint rivers, Georgia ; Suwanee 
River, Florida. 
Unio harperi B. H. Wricut, Naut., XIII, 1899, p. 6. 
Plewrobema harperi Simpson, Pr. Ac. N. Sci. Phila., 1900, p. 
Sr pl. fs. LO; Syl. OOO, ‘p.-750. 
I strongly suspect that this is a mere form of P. bulbosum, 
but I have only seen a very limited amount of material and 
cannot be certain. This differs from that species, so far as 
the material I have seen indicates, in being squarely truncate 
in front, in being more wedge-shaped when viewed from above, 
in having the lateral of the left valve single, and the epidermis 
around the border of the shell more rough. But specimens of 
bulbosum differ so much that these characters may be only in- 
dividual. 
PLEUROBEMA RECLUSUM (B. H. Wright). 
Shell irregularly ovate, inequilateral, subinflated, rather sol- 
id; beaks moderately full and high; their sculpture apparently 
a few strong, irregular ridges that curve up behind; posterior 
ridge strong, subangular, ending below the median line in a 
point ; base line rounded: anterior end subtruncated ; outline of 
the dorsal slope curved; surface nearly smooth; dorsal area 
with a few plications; epidermis greenish-brown, smooth and 
shining; left valve with two ragged pseudocardinals and two 
laterals; right valve with one pseudocardinal and a double lat- 
eral; beak cavities shallow; muscle scars small, impressed; 
nacre brilliant silvery, bluish-tinted, iridescent and thinner be- 
hind. 
Length 4o, height 25, diam. 17 mm. 
Type locality, Ochlocknee River, Leon County, Florida. 
Umo reclusus B. H. Wricut, Naut., XI, 1808, p. 3. 
