220 TESTACEOUS MOLLUSCA. 



what winged, rather inflated, elliptical, inequilateral, thin : beaks 

 scarcely prominent and undulate at tip ; cuticle olive somewhat 

 shining and striate; nacre white. 1^..3^. — Near the Rocky 

 Mountains. 



A. Pepiniana. Lea. on U. 2. p. 96. t. 16. f. 51. Trapezoidal, 

 inequilateral, rather inflated, flattened on the sides, thin, transverse, 

 carinate anteriorly : beaks prominent : umbonal slope rather 

 elevated and rounded : cuticle transversely striated, with the lines 

 of growth strongly marked and apparently without rays ; nacre 

 white. I},. 2. —Ohio. 1 



A. Wardiana. Lea. on U. 2. p. 46. t. 14./. 42. Elliptical 

 transverse, thin, somewhat inflated, inequilateral, at the base sub- 

 emarginate, dorsal margin curved under the beak : umbonal slope 

 rounded : beaks prominent, concentrically undulated at the tip : 

 ligament rather short ; cuticle green, disposed to be yellow on the 

 anterior slope and the beaks : nacre bluish. 1 t 7 q . . 3. — Ohio. 



A. Stewartiana. Lea. on U. fy in Amer. Phil. Tr. 6. 

 Rounded-ovate, very thin, much inflated, anteriorly subangulated, 

 posteriorly short and narrower, dorsal line rather short, nearly 

 straight and forming obtuse angles at both extremities, ventral edge 

 convex ; beaks prominent and granulated at the tip in a short 

 double series ; cuticle ronghish, olive green, obtusely rayed ; nacre 

 bluish white, irridescent, sometimes tinged with salmon colour 

 about the beaks. 2 . . 3 T L. — Louisiana. 2 



A. Grandis. Say. in Transylvania Journal. — A. Corpu- 

 lenta. Cooper. Very large, subovate ; disc unequally wrinkled 

 and undulated transversely, dark yellowish brown : umbo elevated; 

 beak slightly elevated, with generally two or three small sinuous 

 acute undulations ; hinge margin slightly arcuated, sometimes 

 nearly rectilinear, somewhat angulated at its anterior termination, 

 thence the edge descends by a nearly rectilinear or slightly concave 

 line to the anterior margin, which is considerably narrowed ; sinus 

 of the hinge margin concave ; posterior margin widely rounded ; 

 within white margined particularly in front, with dusky. 5 . , 7g« 

 — R, Wabash. 



B. Obovate. 



A. Trapezialis. Lam. U.—Ch.f. 762. — J^. t. 205. /. 1.— 

 Exot. Conch, t. 36. Ovate, fragile, tumid, posterior slope elevated 

 compressed and more winged than the anterior, pale yellowish 

 olive subradiated posteriorly by darker lines : umbones broad, 



1 Add likewise the A. Chaiziana. Rang. 



2 Add likewise the A. Gibbosa of Say. 



