TRIBE NAYADES. 



193 



ventral edge simply arcuated ; umbones not prominent, umbonal 

 slope undefined ; beaks with flexuous undulations; inside bluish 

 white, cardinal teeth oblique, lateral slightly decurved anteriorly. 

 1^ . . 2^. — Delaware, (j'c. N. America.^ 



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

 f. G. Elliptical, transverse, somewhat compressed, inequilateral, 

 thickish, ventral edge rounded; beaks irregularly undulated; cuticle 

 yellow, covered with numerous dark green well defined rays, nacre 

 pearly and pink : cardinal teeth erect, lateral enlarged near their 

 termination. Iy% . . 2^. — Tennessee. 



U. Radiatus. Zam. 13.— U.Virginiana? Lam. 39. — Mya 

 Radiata. Gmel. 3220. — L).p.5\. — Mya Oblongata. Wood. 

 f.2.— Ch.f. 7. Obovate, thin, convex-depressed, very finely striated 

 transversely, the anterior side very broad, cuticle yellowish and lon- 

 gitudinally rayed. 2^. — Sarratoga. 



U. Medellinus. Lea. on tl. 2. (and Tr. Am. b.) p. 39. 

 f. 12. f. 34. Elliptical, transverse, rather compressed, inequilateral 

 thinnish, ventral margin subincurved centrally ; much narrower 

 and obliquely rounded posteriorly ; beaks rather prominent, ligament 

 rather long and slender : cuticle yellowish covered with green rays, 

 nacre white and irridescent : cardinal teeth small, lateral long and 

 somewhat curved. I^^q . . 2^3^. — Vera Cruz. 



U. Notatus. Lea. on V. 2. (Tr. Am. 6.) p. 28. t. 8./. 22. 

 Elliptical, compressed, transverse, inequilateral, anteriorly subbian- 

 gular,thin, posteriorly obhquely rounded : beaks rather prominent : 

 ligament shortish: cuticle reddish brown, covered with interrupted 

 rays, naci'e salmon coloured and irridescent : cardinal teeth small, 

 lateral long and slightly curved. 1 . . 1|^. — Tennessee. 



U. Vanuxemensis. Lea. on U. 2. (and Tr. Am. Q>.) 11 . ./. 

 31. Elliptical, transverse, compressed, inequilateral, thick, ventral 

 edge straightish, anterior edge incurved : beaks somewhat pro- 

 minent : cuticle dark brown and (apparently) rayless, nacre salmon 

 coloured and irridescent : cardinal teeth large, the lateral long and 

 somewhat curved. 1^ , . \-S^. — Tennessee. 



U. Nashvillianus. Lea. Trans. Am. Pit. 5. t. 14. /. 43. 

 Transversely elliptical, thickish, posteriorly rounded and short, ante- 

 riorly produced and subacuminated, ventral and ligamental edges 

 little arcuated: beaks slightly elevated and minutely undulated; 

 ligament shortish : cuticle dark brown, obscurely rayed, nacre 

 pearly white : cardinal teeth lamelliform and double in both valves, 

 the lateral nearly straight. 1 1 . , 2^.— Ohio. 



U. ZiEGLERiANus. Lea. on U. 2. {Tr. Am. 6.) p. 32. /. 10. /. 

 27. Elliptical transverse, inequilateral, smooth, thickish, somewhat 



^ Add likewise the U. Childreni. — Gray. 

 o 



