PLEUROREMA 787 
PLEUROBEMA UTRICULUM (Lea). 
Shell almost elliptical. subinflated or convex, inequilateral, 
rather solid; beaks full and high; anterior end narrowed and 
rounded; base line curved; posterior end obliquely subtrun- 
cated; posterior ridge full, rounded, ending near the base in 
a feeble biangulation; epidermis greenish-brown, showing 
faint, dark rest marks; pseudocardinals small, triangular, two 
in the left valve and one in the right; laterals two in the left 
valve and one in the right ; beak cavities shallow ; nacre bluish- 
white, thinner and iridescent behind. 
Length 43, height 30, diam. 19 mm. 
Type localitv, North Carolina. 
Unio uiriculus Lea, Pr. Am. Phil. Soc., TV, 1845, p. 164; Tr. 
Am Phils Soe., ©, 1848 ip- 69, pl. a, fig. 3; Obs., 1V, 1848, 
pe 4g; pl i figs 3: 
Margaron (Unio) utriculus Lea, Syn., 1870, p. 46. 
Ouadrula utriculus SIMPSON, Syn., 1900, p. 785. 
In the Synopsis I placed this species in Quadrula with a 
question. [ am inclined on giving it additional study to place 
it in Pleurobema near simulans. Its beak cavities are shallow ; 
the pseudocardinals are small and not split up. Lea has two 
shells placed with the type of wtriculus, said to come from Ar- 
kansas, which do not seem to me to be that at all, but are prob- 
ably undescribed. They are so badly worn that I do not think 
it advisable to give diagnosis of them. 
PLEUROBEMA STRODKFANUM (B. H. Wright). 
Shell irregularly short elliptical, subcompressed, scarcely 
subsolid, slightly inequilateral ; beaks moderately full and high; 
posterior ridge well developed, subangulate, ending in a point 
below the median line; anterior end round; base line rounded ; 
outline of dorsal slope almost evenly curved; epidermis closely, 
concentrically striate, cloth-like on the border, shining at the 
umbonal region, nearly jet black; left valve with two pseudo- 
cardinals and two nearly straight laterals ; right valve with one 
pseudocardinal and a double laterai; beak cavities not deep* 
