202 TESTACEOUS MOLLUSCA. 



U. Paranensis. Lea. Tr. Am. Ph. 5. t. 14. y. 42. — U. ^oh- 

 siANA.— D' Orb. in Jtfag. de Z, Subrotund, inequilateral, com- 

 pressed, thickish, umbonal slope flattened ; beaks rather elevated, 

 longitudinally folded and retuse, ligament thin ; cuticle wrinkled, 

 shining, greenish becoming brown towards the margin, with very 

 obscure curved rays which sweep from the beak towards the pos- 

 terior side, nacre pearly white and irridescent: cardinal teeth 

 recurved, double in both valves, the lateral rather long and curved. 

 3 . . Z\. — -S. Parana. 



U. Membranacea. Lea. — Mytilus M. Maton. — Lin. Tr. 

 10. t.24.f. 11, 12.— U. Matoniana. D'Orbig. S. Am. t. 71. 

 J". 1, 2. Roundish, subinflated, posteriorly shorter and rounded, 

 anteriorly angulated, dorsal edge straight, very thin, smoothish, 

 greenish rufous, with very small ribs diverging from the beaks, 

 inside bluish or pink : cardinal tooth thin straight and solitary, the 

 lateral tooth anteriorly very long and elevated. 2 . . 2|^. — S. 

 America. 



U. Variabilis. Lea. — Mya V. Maton in Lin. Trans. 10. t. 

 24. f. 4, 5, 6, 7.—W. t. 3. /. 38.— D. p. 53.— U. Rotundus. 

 Wagn. in Spix. Braz. t. 26. /". 3, 4. Subrhombic gibbous, the um- 

 bones longitudinally wrinkled ; transversely striated, the wrinkles 

 gradually disappearing, cuticle greenish brown, dorsal edge nearly 

 straight, and subangulated at its extremities, ventral edge poste- 

 riorly very obUquely rounded ; nacre bluish : hinge with two teeth 

 diverging at the apex and inserted in linear receptacles. 1 . . 1 — 

 S. America. 



U. Personatus. Say. — U. Capillaris. Lea. Trans. Am. 

 Ph. 5. t. 2.f. 2. Obtusely subquadrate, broader than long, ven- 

 tricose, thickish, subangular and longer anteriorly: beaks thick and 

 elevated, ligament short and thick; cuticle dark and finely wrinkled, 

 smoother towards the beaks, rays numerous capillary and spread- 

 ing, nacre pearly white and irridescent : cardinal teeth much 

 elevated, the lateral lamellar and inclined to curve upwards. 

 \\ . .\^%.^Ohio. 



U. Retusus. La7n. — Conr. Mon. V. t. 8. — Torsa. Raf. in 

 Ann. de Sc. Phy. 5. t. 82. /. 1, 2, S.^Eaton. Obtusely sub- 

 triangular, ventricose, with concentric furrows : beaks subcentral, 

 retuse, umbo very prominent and leaning posteriorly ; ligament 

 long and prominent; umbonal slope rounded and undefined ; pos- 

 terior and ventral edges regularly rounded; anterior side with a 

 slight furrow ; ligamental edge curved and very oblique : within 

 dark purple margined with white : cuticle olive. 2^ . . 2 — 

 N. America. 



U. Ebenus. Lea. Tr. Am. PJi. 4. t. 9. /. 14. — Mytiloides. 

 Conr. {not Bqf.) Obliquely obovate, inequilateral, very ventricose, 

 very thick ; beaks nearly terminal and much elevated, ligament 



