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 . . If. — Tennessee. 



U. LiENOSuSc Conr. in Sil. J. 25. t. \.f. 4. — Con. Mon. U. 

 t. 49./". 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. 2^. — R. 

 Alabama. 



U. Obscurus. Lea. on U. 2. (and Tr.Am. G.)p. 7-t. 3./. 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, 1-rV • • ^' — Tennessee. 



U. Delodontxjs. Lam. — U. Lacteolxjs. Lea. Tr. Am. 5. t. 

 8.y. 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 . . 3^. — La Plata. 



U. Lamellatus. 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^ . • 2f . — Bengal. 



U. Bengalensis. Lea. on U. 2. (and Tr. Am. 6. ) p. 3. t. 2. 

 f. 3. Elliptical, transverse, ineqvulateral, 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. 1 y o • • 2^. — Bengal. 



U. Cceruleus. Lea. on U. \.p. 105. {and Tr. Am. Ph. 4.) 

 t. 13. ,/"• 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 



