176 TESTACEOUS MOLLUSCA. 



U. Trapezoides. Lea. on U. 1. p. 79. t. 3. f. 1. — U. 

 Interruptus. Say, Ann. C, t. 33. — U. Crassidens. Var. 

 A. Lam. 3. Trapezoidal, inequilateral, thick, transverse, ante- 

 riorly angular above and below, posteriorly obliquely rounded ; 

 anterior portion with oblique subparallel large plaits, its slope 

 large and keeled ; beaks slightly prominent, incurved : cuticle 

 black and wrinkled, nacre purple and irridescent : cardinal teeth 

 double in both valves, lateral, curved, and lamelliform. 2J- . . 4^. 

 — Louisiana. 1 



U. Foliatus. Hildreth. in Sil. J. 14. f. 16. — U. Flex- 

 uosus. Conrad, in text. —Foliatus in plate 4 Monog. Com- 

 pressed and shaped like a grape-leaf, the posterior ventral margin 

 having a projecting lobe, on either side of which the edge is 

 incurved anteriorly, rounded posteriorly, beaks flat and eroded, 

 ligament more elevated than the beaks and passing between them ; 

 dorsal margin curved : two elevated ridges from the beaks pro- 

 jecting on the anterior dorsal and ventral margins : cuticle dark 

 olive, waved transversely, and obscurely rayed with green across 

 the waves : cardinal teeth small, that in the right valve deeply 

 sulcated, the lateral teeth short and thick : nacre greenish white. 

 2. — United States. 



U. Pliciferus. Lea. on U.2.p. 61. t. \7.f. 53. Elliptical, 

 inequilateral, somewhat inflated, with numerous small folds on the 

 anterior side and slope, thicker posteriorly : ligament short and 

 light horn coloured, cuticle blackish green, nacre purple : teeth 

 rather large, the lateral straight. \^ . . 2^. — Mexico. 



U. Multistriatus. Lea. on U. 1. p. 101. t. 12. /. 22. 

 Subrectangular, transverse, inequilateral, slightly compressed and 

 rounded nearly alike at both ends, rather thin ; beaks slightly 

 prominent, surrounded by wrinkles forming acute angles with each 

 other : ligament linear ; cuticle dark brown and wrinkled, nacre 

 bluish white : cardinal tooth oblique, lamelliform, single in the left 

 and double in the right valve, the lateral long and nearly straight. 

 1 .. 1 T %.— Brazil. 



U. Subtentus. Say. J.A.N. S. Phil. 5. fy Am. Con. t. \5. 

 Oblong-oval, subcompressed, slightly contracted at the middle of 

 the base, dull yellowish brown ; beaks not prominent, decorti- 

 cated : dorsal edge regularly arcuated, without any appearance 

 of an angle : anterior margin with numerous slightly reflected 

 ribs. 1|- . . 3^. — North America. 



U. Conradicus. Lea. Trans. Am. Ph. 5. t. 9. f. 23. 

 Elongated-elliptic, transverse, rounded and short posteriorly, attenu- 

 ated anteriorly, ligamental edge straight, ventral entire and little 



1 Lamarck's Castali^e belong to this section. 



