•tribe nayades. 201 



U. Littoralis. Lam. 25.— Crassus. Schr. F. 2, f. 2. — 

 Rhomboidea. Schr. 2. f. 3. — Brevialis, Semirugata, and 

 Nana. Lam. 14, 16, fy 17. {fide Lea). — Incurvus. Lea. on 

 U. 1. p. 167. t. 13. /. 27. Transverse, oval, thick, dark brown, 

 inequilateral, transversely striated, posteriorly rounded, anteriorly 

 produced, ligamental edge sloping, ventral edge little arcuated, sub- 

 incurved: anterior slope with a marginal groove on each side: 

 beaks wrinkled: cardinal teeth thick, conical, dentato-serrated, the 

 lateral thick. 2\. — France, fyc. 



■f f f f f Subrotund, 



U. Circulus. Lea. Tr. Am. Ph. 3. t. 9.f. 14.— Eat.— Mya 

 Rotunda ? — Wood. Circular, ventricose, subequilateral, thick, 

 transversely wrinkled ; beaks rather elevated and somewhat re- 

 curved ; ligament short and thick ; cuticle dark brown becoming 

 light yellowish brown anteriorly, shining and satinlike, nacre pearly 

 white and irridescent : teeth large. Diameter, 1^-. — Ohio, fyc. 



U. Lens. Lea. on U. I. p. 90. (andTr. Am. Ph. 4.) t. S.f. 10. 

 Lenticular, broader than long, subventricose, equilateral, thickish, 

 beaks slightly prominent, undulated at the tip, ligament short and 

 thick: cuticle smooth brown but anteriorly yellowish, nacre white 

 rarely rosy : cardinal teeth large, the lateral short and straightish. 

 T 9_.. 1 1. — Ohio. 



U. Rubellus. Conr. N. F. W. S. p. 38. t. 6. /. 2. Sub- 

 orbicular, transverse, ventricose, thick, subequilateral, umbones 

 prominent, umbonal slope rounded, margined before and behind 

 by a faint angle ; beaks eroded, slightly prominent ; cuticle 

 reddish brown, nacre pink or purplish: cardinal teeth direct. — 

 It. Alabama, 



U. Masoni. Conr. N. F. W. S.p. 34. t. 5.f. 2.— Con. Mon. 

 U. t. 12. f. 2. Transverse, suborbicular, discs slightly flattened ; 

 umbones broad prominent, carinated behind : beaks slightly promi- 

 nent : umbonal slope straight and angulated, ligament slope flat- 

 tened and broad: cuticle olive, clouded with brown and polished, 

 nacre bluish white : cardinal teeth prominent, compressed very 

 oblique: f. — P. Savannah, N. America. 



U. Rotundatus. Lam. — Suborbiculata. Lam. fy Bl. — 

 U. Glebulus. Say. Am. Conch, t. 34. — Subglobosus. Lea. 

 Tr. Am. Ph. 5. t. 2.f. 3. Transverse, obovate, inflated, thick, pos- 

 teriorly rounded and shorter, anteriorly subangulated, ventral edge 

 arcuated and somewhat sinuated anteriorly ; beaks slightly promi- 

 nent, rounded ; umbonal slope carinate, ligament thick and shortish: 

 cuticle dark brown or black, nacre pearly pink ; cardinal teeth 

 wide and striated, the lateral somewhat curved. 2-£$ . . 1 t °q. — 

 Louisiana. 



