762 PLEUROBEMA 
pseudocardinals small, triangular, two in the left valve, three 
in the right; laterals two in the left valve and a double one in 
the right ; muscle scars small, impressed ; beak cavities shallow ; 
nacre white. 
Length 37, height 29, diam. 22 mm. (type) 
Length 45, height 30, diam. 23 mm. 
Coosa River system; Columbus, Georgia ? 
Type locality, Connasauga Creek, Whitfield Co., and Eto- 
wah River, Ga. 
Umio murrayensis Lea, Pr. Ac. N. Sci. Phila., II, 1868, p. 143; 
ji- Ac N. Sct; Philay Vl 18605 pp: 403) pl xiva tio, pense 
Obs; So 1860, p62, plaxivi, hes Mis: 
Margaron (Unio) murrayensis L&A, Syn., 1870, p. 40. 
Pleurobema murrayensis SIMPSON, Syn., 1900, p. 753. 
The type, whose dimensions | have given above, is not as 
elongated as most specimens of this species are. The shell is 
shorter than chattanoogaense, it 1s solider and more inflated 
than imterzentum and is duller colored than either. It is close 
to the troschelianum group. 
Group of Pleurobema curtum. 
Shell elongate, triangular, truncated in front, rounded on 
the base, where it is quite full behind the middle, with a low 
posterior ridge, the space between the middle of the disk and 
the ridge flattened or sometimes slightly excavated, rather 
sharply pointed behind ; umbonal region very prominent ; beaks 
well forward: beak sculpture not observed; epidermis rather 
smooth, brownish-olive; pseudocardinals distinct, triangular, 
radiate; laterals heavy, slightly curved: cicatrices small and 
deep ; nacre iridescent posteriorly. Animal with the gills large, 
semicircular, the outer slightly larger than the inner, which 
are free nearly their whole length from the abdominal sac; 
marsupium occupying the entire length of the outer gills. 
PLEUROBEMA CURTUM (Lea). 
Shell subtriangular, solid, inflated, the beaks high and full, 
placed nearly or quite at the anterior end, which below them 
is squarely truncated; outline of dorsal slope nearly straight ; 
