186 TESTACEOUS MOLLUSCA. 



f. 40. Sub triangular, inflated, subequilateral, depressed before the 

 umbonal slope which is carinated, thick, anteriorly angular, the ven- 

 tral margin emarginate : beaks prominent, incurved and slightly 

 undulated at their tips : ligament short and thick : cuticle brown, 

 rays obsolete, nacre pearly white and irridescent : cardinal teeth 

 large, lateral large and slightly curved. 2 . . 2^. — Ohio. 



U. Solidus. Lea. on U. 2. p. 13. (§• Tr. Am.) t. 5.f. 13. 

 Oblique, inflated, very thick inequilateral : beaks very elevated and 

 retuse ; ligament shortish and thick ; cuticle rusty green, (some- 

 times obscurely rayed) nacre pearly white : cardinal teeth thick, 

 lateral oblique and short, l^g- . . 1 J, — Ohio. 



U. Obliquus. Lam. — U. Undatus. Barnes in Sil. J. 6. t. 4. 

 f.A. — Trigonus. Say. fy Conr. — Cordatus. Conr. Mon. U.t. 

 25. Sub triangular, longer than broad, thick, very tumid, posteriorly 

 obtuse and very short, anteriorly rapidly narrowed and angulated : 

 beaks elevated and recurved, with the ligament passing between 

 them ; ventral edge compressed in the middle ; cuticle horn 

 coloured and glabrous, nacre pearly white : cardinal teeth deeply 

 sulcated and crenated, two lateral ones in each valve. 24- . . 2-rW. — 



TkT A • 5 10 



iV. America. 



U. Pyramidatus. Lea. on U. 1. p. 119. ($* Tr. Am. 4.) t. 

 16. /. 39.— U. Mytiloides. Raf.~ Mya Obliqua. Wood. S. 

 t. 2.y. 8. Subpyramidal, longitudinal, inflated, oblique posteriorly 

 thicker, swollen and very short, beaks very much elevated, recurved 

 and incurved : cuticle dark brown and finely wrinkled, nacre flesh 

 colour ; cardinal teeth large and crenated, the lateral long, distinct 

 from the cardinal and pointing ventrally. 2 T % . . %£$• — Ohio. 



t f Oblique. 



U. Troostensis. Lea. Trans. Am. Pit. 5. t. 10. f. 30. — 

 U. Trabalis. Conr. Mon. U. p. 110. t. 60. f. 2. Oblong-ovate, 

 ventricose, posteriorly short and rounded, anteriorly produced 

 attenuated obtusely cuneiform, ventral edge slightly arcuated and 

 entire : umbonal slope rounded, anterior slope flattened or concave 

 (in old shells furrowed) ; beaks eroded and rather prominent ; 

 cuticle smooth, polished, dark olive tinted with green, with dark 

 green unequal rays : within dull white or slightly salmon coloured 

 posteriorly, bluish and very irridescent anteriorly, cardinal tooth in 

 one valve very thick and direct. 1^ . . 1^. — JV. America. 1 



U. Taitianus. Lea. Tr. Am. Ph. 5. t. 4. f. 11. Subtrian- 

 gular, thick (particularly posteriorly), depressed posteriorly to the 

 umbonal slope, beaks very thick and much elevated ; cuticle dark 

 brown and wrinkled, nacre pearly white : cardinal teeth large and 

 elevated, the lateral thick and slightly curved. \\..\\. — P. 

 Alabama. 



1 Add likewise the U. Tigris of Ferussac. 



