I EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



Inocbramus Simpsoni, Meek. 



Plate 4, fig. 4. 

 ramm simpsoni, Meek (July, 1860), Proceed. Acad. Nat. Sci., Philad., XII, 312. 



Shell attaining a large size, transversely elongated or narrow, oval, gibbous in the 

 and anterior regions, cuneate posteriorly; anterior side rounded ; anal side 

 very long, usually broader than the other, and sul (truncate at the extremity; base in 

 young shells semiovate, being more convex behind than in front, in large specimens 

 rounding up very gradually toward the front, and apparently a little contracted or 

 slightly sinuous behind: hinge straight, long, and ranging nearly parallel to the longer 

 axis of the valves: beaks vising little above the cardinal border, rather convex, located 



regular concentric undulations, which sometimes bifurcate on the flanks; lines of 



Length, 8.10 inches; height, 4.35 inches; convexity, about 3.72 inches. 



The remarkably elongated transverse form of this shell will serve to distinguish 

 it from any other species yet known in our rocks, resembling it in other respects- 

 Goldfuss figures a somewhat similar form (Taf. cxii, fig. 4 d, Petrefact. Germ.) under 

 the name of /. Criptii, Sowerby ; though the identity of the specimen from which his 

 figure was drawn with Sowerby's species seems to be doubtful. At any rate, it differs* 

 from that now under consideration, in having more pointed beaks, which are much 

 more remote from the anterior end of the shell ; it is likewise broader posteriorly than 



In the position and oblitpiity of its beaks, as well as in some other respects, J 



found associated with /. Iimahini, var. cantatas. 



The specific name of this fine Inoceramw was given in honor of C apt. J. H. Simp- 

 son, commander of the explorations across the Great Basin of Utah. 



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

 No. 3 of the Upper Missouri Cretaceous series. 



BEAR RIVER FRESH-WATER OR ESTUARY BEDS. 



In first preparing this report (in 1860), I referred the fossils from the above-men- 



the localitv, however, as elsewhei 

 ably upper beds of the Cretaceoi 

 them together here in a separate < 



