184 TESTACEOUS MOLLUSCA. 



angular, very thick, ventricose, umbones flattened, beaks promi- 

 nent and rounded, umbonal slope angulated ; anterior margin flat- 

 tened, a broad convex elevation marked with radiating prominent 

 lines (vk^hich dentate the margin) and concentric grooves projecting 

 ventrally : cuticle olivaceous and wrinkled, nacre very white : liga- 

 ment very short : cardinal teeth double in both valves, thick, 

 prominent sulcated and granulated. 2j. — R. Alabama. 



U. Securis, Zea. on. U. 1. p. 5\. t. \l. f. 17. — H^at. — U. 

 Depressa. HaJ". not. Lam. Subtriangular heart-shaped, in- 

 equilateral, flattened over the umbones, thick ; beaks elevated, 

 recurved, much compressed : ligament shortish and thick : cuticle 

 olive yellow passing into olive brown, shining and transversely 

 wrinkled, nacre pearly white and irridescent. 1^ . . 1to'~ Ohio. 



U. Camelus. Lea. Trans. Am. Ph. 5. t. 15. f. 45. Trans- 

 verse, subtriangular, thick ; rounded, short and very attenuated 

 posteriorly ; flattened over the umbones from the beaks to the 

 ventral margin, which is little arcuated and incurved in the 

 middle ; anteriorly subcuneiform, cuticle yellowish brown with 

 capillary rays, nacre white ; cardinal teeth small, the lateral large 

 thick and curved. 2-^^ . . 3f . — Ohio. 



U. OvATus. Say. in Enc. Am. Nich. — Lam. — Conr. Mon. 

 2. f. 1, 2, 3. — Barnes, Obovate, convex, not thick, deeply 

 wrinkled, glossy, umbones prominent, epidermis yellowish or 

 horn coloured, rayless ; anterior slope flattened and fuscous, some- 

 what waved with striee, and wrinkles which become lamellar : 

 hinge-margin making an angle with the anterior and posterior 

 dorsal edges ; nacre pearly, bluish white : beaks subcentral, 

 recurved; teeth elevated, the cardinal compressed and crestlike. 

 2^^..3^^.~Ohio. 



U. SuBOVATUs. Lea. on U. 1. p. 128. t. 18. /. AQ. Sub- 

 ovate, transverse, inflated, thick, inequilateral : beaks elevated, 

 incurved and undulated at the tips ; ligament short and thick : 

 cuticle yellowish with numerous oblique green rays, nacre white 

 and very pearly : cardinal teeth double in both valves and erect, 

 the lateral short and lamelliform. 3 . . 4i. — Ohio. 



U. Crassidens. Lam. — U. Niger. Co7ir. Mon. U. t. 

 26. — U. CuNEATus. Barnes. Elongated and subtriangular, 

 ponderous, anteriorly narrowed wedge-shaped and compressed ; 

 umbones somewhat elevated, beaks low and distant : anterior de- 

 pression elongated, heart-shaped and furrowed, the ventral edge 

 slightly rounded : cuticle blackish brown, somewhat ferruginous : 

 an elevated ridge from the beaks anteriorly : nacre brownish 

 purple and irridescent ; cardinal teeth deeply divided and sulcated, 

 the lateral long curved and not thick. 2^^ . . 3^. — North 

 America. 



U. Carbonarius. Lea. on. U. 2. p. 37. U^ in Tr. Am. Ph. 4.) 



