186 TESTACEOUS MOLLUSCA. 
f. 40. Subtriangular, 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 .. 2-3;.— Ohio. 
U. Soxipus. 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. 1-75 ..14.— Ohio. 
U. Osriauus. Lam.—U. Unpatus. Barnes in Sil. J. 6. t. 4. 
f.4.—Triconvus. Say. § Conr.—Corvatvus. Conr. Mon. U.t. 
25. Subtriangular, 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;45.— 
N. America. 
U. Pyramipatus. Lea. on U. 1. p. 119. (§ Tr. Am. 4.) t. 
16. f. 39.—U. Myrimorpes. Raf.—Mya Osriaua. Wood. 8. 
t.2. f.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. 253,..23!5.— Ohio. 
++ Oblique. 
U. Troostensis. Lea. Trans. Am. Ph. 5. t. 10. f. 30.— 
U. Trasauis. 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 direet. 11..13.—N. America.} 
U. Tartianus. 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. 12..13.—WR. 
Alabama. 

1 Add likewise the U. Traris of Ferussac. 
