312 PKOOEEDINGS OP THE ACADEMY OF 



Meek & Hayden, and a small Inoceramus. Probably of lower Cretaceous 

 age, but may be older. 



Inoceramus Simpsoni, Meek. Shell attaining a large size, transversely 

 elongate, or narrow, oval, gibbous in the umbonal and anterior regions, cuneate 

 posteriorly ; buccal side rounded ; anal side very long, usually broader than 

 the other, and subtruncate at the extremity ; base in young shells semiovate, 

 being more convex behind than in front, in large specimens rounding up very 

 gradually towards the front, and apparently a little contracted, or slightly 

 sinuous behind ; hinge straight, very long ; beaks rising little above the car- 

 dinal border, rather convex, located very near the anterior extremity ; surface 

 ornamented by moderately distinct, rather regular, concentric undulations, 

 which sometimes bifurcate on the flanks ; lines of growth small, regular, and 

 equidistant. Length 8*10 inches ; height; 4-35 inches ; convexity about 3*72 

 inches. 



The specific name of this fine Inoceramus is given in honor of Capt. J- H. 

 Simpson, of the U. S. Top. Engrs., commander of the explorations for the 

 location of wagon routes in Utah, &c. 



Locality and position. North Platte above the bridge, from the horizon of 

 No. 2 or 3, of the Nebraska cretaceous series. 



TERTIARY SPECIES. 

 CONCHIFERA. 



Unio vetusta, Meek. Shell rather thin, of medium size, narrow, much 

 elongated transversely, moderately convex ; anterior side rounded ; basal and 

 dorsal margins nearly straight and parallel ; posterior side very long, more 

 compressed and rather narrower than the other obliquely truncate above, and 

 angular below in young shells, but becoming more rounded with age ; beaks 

 small, much depressed ; located near the anterior end ; surface of young speci- 

 mens ornamented by fine, regular, concentric wrinkles, crossed on the umbo- 

 nal slopes of each valve, by two sharply defined angles, which radiate from 

 the beaks nearly or quite to the posterior extremity. On old and medium 

 sized specimens, these markings become nearly or quite obsolete, excepting 

 sometimes near the beak. Length of a large specimen 3 '22 inches ; height 

 1*30 inches ; convexity about 0-60 inch. 



Locality and position. Brackish-water deposits on Bear River near the mouth 

 of Sulphur Creek, lat 41 12' north, long. 110 52' west. 



Unio Haydeni, Meek. Shell small, subelliptical, rather thin, moderately 

 convex ; extremities more or less regularly rounded, the posterior margin 

 being sometimes obliquely subtruncate above, and more narrowly rounded 

 below than the other ; basal border semi-elliptical in outline ; dorsal side 

 nearly straight along the middle ; beaks very small, depressed nearly to a 

 level with the dorsal margin, not eroded, and apparently without wrinkles, 

 located about half way between the middle and the anterior end ; posterior 

 umbonal slopes rather prominently rounded ; surface smooth, or only showing 

 obscure marks of growth. Length 1*65 inches ; height 1 inch ; convexity 0-60 

 inches. 



Locality and position. Freshwater Tertiary beds, near Fort Bridger, and 

 south of there, at the base Uintah Mountains, lat. 41 40' north, long. 110 

 10' west. 



Corbula (Potamomya ?) pyriformis, Meek. Shell transversely pyriform, 

 moderately thick, very gibbous in the anterior and umbonal regions, more 

 compressed and subrostrate behind ; buccal side truncate above from the beaks 

 obliquely forward, rounding rather abruptly into the base below ; posterior 

 side much narrower, and longer than the other, and very sharply rounded or 

 slightly truncate at the extremity ; base semiovate, being much more promin- 

 ent in the central and anterior regions than behind ; dorsal outline declining 



[July, 



