178 TESTACEOUS MOLLUSCA. 
U. Asperrimus. Lea. on U. 1. p. 81.t.5.f.3.—Tr. Am. Ph. 
4.t.5.—U. Quaprutus. Say. Am. Con. t. 53. Subquadran- 
gular, thick, inequilateral; anteriorly biangular, with a broad 
smooth obtuse keel from the elevated beaks to the ventral margin, the 
slope and also the posterior edge of the keel nodulous: cuticle 
fuscous (in the young, yellowish brown with obsolete rays) nacre 
pearly and irridescent : cardinal teeth very large, lateral large and 
nearly straight. 33..44.—Ohio. 
U. Tracosus. Conr. Mon. U. p. 12. t.6. f. 2. Suborbicular 
inclining to subquadrate,subequilateral, ventricose ; anterior margin 
direct and obtusely forming an angle with the oblique and nearly 
straight ligamental edge; with an indistinct narrow furrow (form- 
inga deep sinus at its termination) and two approximate series of 
very prominent irregular tubercles, anterior slope slightly concave, 
with a few narrow rib-like tubercles more prominent near the 
margin ; umbo narrow, prominent ; beaks much incurved, pointed, 
tuberculated : cuticle brown, usually with two or three broad, 
widely interrupted green rays. 2..21.— Ohio. 
U. Paruipsi1. Conr. Mon. t. 5. f. 1. p. 9. Subovate, pos- 
teriorly rounded ; anterior side narrowed angulated above and 
below with a wide furrow and a few small tubercles, extremity 
subincurved : umbonal slope straight, subcarinated and tubercu- 
lated ; anterior slope concave, indistinctly tuberculated ; ligamental 
edge oblique, rectilinear : ventral edge swelling centrally incurved 
in front ; cuticle yellowish brown, with indistinct filiform rays over 
the rather prominent umbo, disc with a single row of irregular 
tubercles in the centre, some of which are elongated and grooved : 
inside white, cardinal teeth rather small, direct, double in each 
valve. 13..2.—R. Wabash, N. America. 
U. Pusrutatus. Lea.on U. 1. p. 89.t. 7. f. 9. Rounded- 
obovate, transverse, equilateral, inflated, thick, simply rounded 
posteriorly, the granulated anterior and the anterior ventral edge 
incurved : with two vertical rows of tubercles, one nearly central, 
the other along the umbonal slope; beaks elevated, ligament short 
and thick; cuticle yellowish brown, nacre white and irridescent : 
cardinal teeth large, lateral short and straightish. 159,. . 2;15.— Ohio. 
U. Scuootcrarrensis. Lea. Tr. Ph. Am.t. 3. f. 9.—U. 
Prastnus. Conr. ‘Transversely obovate, compressed, thickish, 
slightly tuberculated behind the umbonal slope, anteriorly longer 
and angulated above and below; beaks elevated, ligament short : 
cuticle yellow with the rays green and broad (particularly the 
central one) ; nacre pearly white and irridescent; cardinal teeth 
elevated, the lateral straight and lamellar. 1,1,..1-3,.—V. 
America. 
U. Apicutatus. Say. Am. C. ¢. 52. Subquadrate, the dia- 
meters subequal, obtusely subangulated, compressed and rather 
