TRIBE NAYADES. 195 



teeth laraelliform and double in the right valve only, the lateral 

 straight. A. . 1|.— i?. Hoogly, Hindostan. 



U. Olivarius. Lea. on U. I. p. 118. (and Tr. Am. Ph. 4.) 

 t. 16. f. 38. — Benson. Ovate-oblong, transverse, inequilateral, 

 very thin, pellucid, smooth, anteriorly subattenuated, ventral edge 

 somewhat rounded; beaks slightly elevated, rounded, not undulated ; 

 ligament very small, cuticle olive, very smooth, rays obscure, nacre 

 white and pearly : cardinal teeth large erect and lamelliform, lateral 

 short and lamelliform. i . . 1^. — India. 



U. Batavus. Lam. 33. — Schroet. F'luss. t. 3. f. 5. — E. t. 

 248. f. 3. Ovate, tumid, shaded off from green to yellow, rayed, 

 posterior side very short ; anterior obliquely curved, the extremity 

 rounded, -ft. Seine, ^'c. — Thicker and more obtuse at the extre- 

 mities than Pictorum.^ 



U. CuMBERLANDiANUs. Lea. 071 U. 2. (and Tr. Am. 6.) 

 23. 25. t. ?•,/' 19. Elliptical, transverse, inequilateral, thin, ventral 

 edge rounded ; beaks somewhat prominent, ligament short ; cuticle 

 yellow with numerous subequidistant narrow gi'eenish rays, nacre 

 white and irridescent : cardinal teeth small, lateral long and 

 straight. 4 . . l^. — Tennessee. - 



U. ViBEx. Conr. N. F. W. S. 31. t. 4./. 3. Elliptical, ven- 

 tricose, thinnish, anteriorly dilated, very oblique and arcuated, 

 posteriorly rounded but angulated on the dorsal edge : ligament 

 margin slightly elevated, umbonal slope rounded : cuticle yellowish 

 olive, clouded with brown, anteriorly with green interrupted linear 



1 Mr. Lea in his synopsis of Uniones, (a work whose outlines are 

 but filled up in the present monograph), gives as synonyms of this 

 deceptive species. 



<*U. Batavus of Fleming, PfeifFer, Wood, Maton, Dilwyn, 

 Turton — Pictorum of Montagu and of Draparnand, t. ll.y. 3. — 

 U. Riparia and Gibba of PfeifFer. — U. Sinuatus and Planus of 

 Studer.— U. Fusculus of Muhl. — U. Reniformis, Schmidt.— U. De- 

 curvatus, Rossmasler. — U. Fuscus, Consentaneus and Amnicus 

 Zieg." — I am afraid that Mr. Lea is scarcely correct in his ideas of 

 our European Uniones. Assuredly the above synonyms seem to me 

 so strangely united, that I have not ventured to add one iota to the 

 brief description and scanty references of Lamarck. As this shell 

 has been generally considered British, from trusting to the figures 

 in Wood and Turton, it may be as well to observe, that I have 

 reason to believe that the former was copied from Schrceter's Fluss- 

 conchylien, t. 3. _/. 4. (and not from a British shell), whilst the 

 latter is stated by Mr. Gray, to have been delineated from the 

 former. 



2 Add likewise the U. Smithii. — trray. 



