194 TESTACEOUS MOLLUSCA. 
prominent, with fine undulations at the tip; ligament shortish : 
cuticle yellow, anteriorly with linear green rays, nacre purple and 
irridescent ; cardinal teeth small, the lateral small and straightish. 
1. .13.—- Tennessee. 
U. Liznosus. Conr. in Sil. J. 25. t. 1. f. 4.—Con. Mon. U. 
t. 49. f. 1. Narrow-elliptical, ventricose, posteriorly thick short 
and rounded, anteriorly abruptly rounded at the ventral edge 
(which is little curved and entire) and subangulated at the end : 
beaks approximate, little elevated and corrugated ; concentric lines 
coarse and prominent ; cuticle very dark olive, and obscurely rayed, 
nacre from bluish white to deep salmon or purple: cardinal teeth 
oblique, rather compressed and double in both valves. 24.—R. 
Alabama. 
U. Osscurus. Lea.on U. 2. (and Tr. Am. 6.) p.7.t. 3. f. 7. 
Elliptical, transverse, inequilateral subinflated, thickish, ventral mar- 
gin and anterior dorsal edge straightish ; beaks irregularly undulated : 
cuticle yellowish brown, with linear darker rays anteriorly, nacre 
purple and white: cardinal teeth elevated, the lateral larger near 
their termination. 154,..2.— Tennessee. 
U. Detovontus. Lam.—U. Lacreouvs. Lea. Tr. Am. 5. t. 
8. f.19. Elliptic, transverse, not thick, subinflated, posteriorly short 
narrow rounded, angulated anteriorly ; beaks rounded, having short 
radiating folds, ligament shortish : cuticle dark brown and wrinkled, 
nacre pearly and milk white; cardinal teeth long and double in 
both valves, the lateral long and separate. 2..31.—La Plata. 
U. Lametuatus. Lea. on U. 2. (and Tr. Am.6.) p. 19. t. 6. 
f. 16. Subovate, transverse, subinflated, glossy, very thin, dorsal 
edge straightish, angular at its extremities ; posteriorly much nar- 
rower and the ventral margin oblique and rounded : umbonal slope 
with two capillary subparallel raised lines : beaks scarcely prominent, 
minutely undulated : cuticle dark brown and rayless, nacre bluish : 
cardinal teeth long, thin, and lamellar, the lateral long thin and 
nearly straight. 1}. .23.—Bengal. 
U. Bencatensis. Lea. on U. 2. (and Tr. Am.6.) p. 3. t. 2. 
f. 3. Elliptical, transverse, inequilateral, rather inflated, very 
thin, dorsal edge angular at both ends, ventral edge subincurved: 
beaks minutely undulated ; cuticle reddish brown, obscurely rayed : 
nacre purple: cardinal teeth thin and lamellar, the lateral rather long 
and linear. 13,..21.— Bengal. 
U. Caruteus. Lea. on U. 1. p. 105. (and Tr. Am. Ph. 4.) 
t. 13. f. 25.—Benson. Narrow elliptical, transverse, inequilateral, 
subcylindraceous, thin, ventral margin centrally straightish, dorsal 
edge anteriorly straight; beaks rather elevated, rounded, and undu- 
lated ; cuticle finely wrinkled and bluish green particularly anteriorly, 
rays very indistinct ; anterior slope with small undulations, and two 
irregular rays; nacre bluish white, pearly and irridescent: cardinal 
