TRIBH NAYADES. 



203 



rather short and thick : cuticle blackish brown before the beaks 

 and at their tip, on the second growth yellow, nacre pearly white: 

 cardinal teeth large, lateral large and curved. 1 J . . If. — Ohio. 



U. Maculatus. Conr. N. F. W. S. p. 30. t. 4. /. 4. Sub- 

 triangular, compressed, thickish ; cuticle much wrinkled except on 

 the smooth umbones, brown olive with a few very broad and narrow 

 intervening interrupted green rays ; a slight broad and oblique 

 furrow from the prominent beaks to the base : umbonal slope sub- 

 angulated, behind which the shell is cuneiform, ligament edge ob- 

 lique, rectilinear, anterior edge obliquely subtruncated : cardinal 

 teeth nearly transverse, subcompressed : nacre very white and irri- 

 descent. — Tennessee. 



U. Kirklandianus. Lea. Trans. Am. Ph. 5. t.lA.f. 41. 

 Rounded-subquadrate, broader than long, thick, compressed, ante- 

 rior and ligamental edges little arcuated ; beaks somewhat elevated, 

 ligament thick and rather short ; cuticle wrinkled, dark brown 

 but yellowish near the beaks, with interrupted rays not reaching 

 the well rounded ventral edge, nacre pearly white and irridescent : 

 cardinal teeth thickish, the lateral short and slightly curved. 



2.. 2yV— 0ki0 - 



U. Subrotundus. Lea. Tr. Am. Ph. 4. t. 18./. 45. — Poli- 

 tus ? Say. — Suborbicular, subventricose, thick, subequilateral, 

 beaks thick and elevated, ligament thick and shortish ; cuticle 

 yellow and smooth towards the beaks, becoming brown and finely 

 wrinkled towards the margin, with interrupted rays about the 

 umbones, nacre white and irridescent : cardinal teeth thick, the 

 lateral short and slightly curved. Diameter, If. — Ohio. 



U. Infucatus. Conr. F. N. W. S. p. 45. t. 3.f. 2. Trans- 

 versely obovate, compressed ; anteriorly dilated, the margins 

 slightly oblique, obtusely rounded or subangulated at its extremity; 

 umbones wide, not prominent, beaks greatly eroded ; umbonal slope 

 subangulated and hardly curved : cuticle black, nacre pearly white : 

 cardinal teeth direct, pyramidal. — Georgia in America. 



U. Coccineus. Lea. on TJ. 2. (and Tr. Am. 6.) p. 12. t. 5. 

 f. U.—Conr. Mon. U. t. 13. /. 1.— Catillus. Conr. Mon. TJ. 

 t. 13. f, 2. Subtriangular, oblique and slightly compressed, thicker 

 posteriorly, posterior dorsal edge very short and sharply angulated ; 

 beaks rather elevated retuse, with one or two undulations ; liga- 

 ment rather long and curved : cuticle dark reddish brown, nacre 

 bright red : cardinal teeth thick, the lateral thick and somewhat 

 curved. 2 . . 2f. — Ohio. 



ttttttt Wide. 



U. Shepardianus. Lea. Trans. Am. Ph. 5. t. 13. f. 38. — 

 Very elongated transversely, thickish, short and rounded poste- 



