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. 

 H • • 2 J. — Delaware, #c. N. America, 1 



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

 f. 6. 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. 1^ . . 2f . — Tennessee. 



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

 Radiata. Gmel. 3220. — D. p. 51.— 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 U. 2. (and Tr. Am. 5.) p. 39. 

 t. 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, l-^ . . 2-^.— Vera Cruz. 



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

 Elliptical, compressed, transverse, inequilateral, anteriorly subbian- 

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

 ligament shortish: cuticle reddish brown, covered with interrupted 

 rays, nacre salmon coloured and irridescent : cardinal teeth small, 

 lateral long and slightly curved. 1 . . If.— Tennessee. 



U. Vantjxemensis. Lea. on U. 2. (and Tr. Am. 6.) 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. If . . 1^.— Tennessee. 



U. Nashvillianus. Lea. Trans. Am. Ph. 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. 



\5. Zieglerianus. Lea. on U. 2. {Tr. Am. 6.) p. 32. 1. 10. /. 

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



1 Add likewise the U. Childreni.— Gray. 



o 



