I 



/. Hall on the Cretaceous Strata of the United States. 81 



/ 



In a paper recently publislied in the Proceedings of the Acad- 

 emy of Natural Sciences by Messrs. Meek and Ilayden, speaking 

 of tlie geographical distribution of the cretaceous fossils, they 

 refer to the well known species, Ammonites i^T^acenta^ Scaphites 

 Conradij Bacidites ovaius^ and Nautilus Dtkayi^ as being common 

 to the central or upper portions of the New Jersey cretaceous 

 strata, to the "Rotten limestone" of Alabama, and to beds Nos. 4 

 and 5 of Nebraska. Alluding to the position of the cretaceous 

 beds of the southwest, thcv remark : — 



'^ At the same time, the total absence of the above named fos- 

 sils, and indeed so far as we yet know, of all the other species of 

 J^ the lowest and upper two Nebraska cretaceous formations, in the 



rocks from which Roemer and others collected so many species 

 in Texas, and other southern localities, renders it highly proba- 

 ble that if the latter occur at all in Nebraska, they must be rep- 

 resented by the beds Nos. 2 and 3 of our section. This conclu- 

 sion is further strengthened hy the fact, that the only Nebraska 

 species yet found in the southwest, so far $s we know, are Inoc^- 

 ramus prohlematicus and Ostrea congesla, both of which are un- 

 known in the northwest, excepting in the above named beds, 

 and are mainly restricted to the kfter. The well marked specific 

 characters of these two fossils, and their limited vertical range, 

 together with their extensive geographical distribution, renders 

 the bed in which they occm' a horizon of the highest importance 

 in the identification of strata at reinotely separated localities in 



these far western territories. 



" That these beds or formations of the same age, are widely dis- 

 tributed over a vast area of country, extending from near the 

 Great Bend of the Missouri in lat. 44^ 15', long. 99^ 20', west- 

 ward to, and perhaps beyond, the eastern slope of the Rocky 

 Mountains, and far south into Texas and New Mexico, is highly 

 probable, from the occurrence of these characteristic fossils at 

 many widely separated localities in this region. At any rate, we 

 1^ know, from information obtained through Mr. Ilenry Pratten, of 



the Geological Survey of Illinois, that Inoceramns ^rohlematicus 



\ 



is found in a light-colored limestone overljnng a red sandstone 

 on Little Blue River, a tributary of Kansas River. Col. Fre- 

 mont also collected specimens of the same shell from a similar 

 rock on Smoky Hill River, in lat. 39°, Ion. 98^, and at other lo- 

 calities between there and the Rocky Mountains.^ More recently 

 Lieut. Abert found the 

 point as far southwest as 



apparently on the western declivity of the anticlinal axis of the 

 Rocky Mountainsf. Roomer likewise collected in Texas speci- 

 mens of a shell he refers to Inoceramus mytiloides of Mantell, 



* See Prof. Hall's Figures and Remarks in Fremont's Report, p. 1T4, PL 4 

 f Lieut. Abert's Report of Explorations in New Mexico and California, p. 54t. 



SECOND SERIES, VOL. XXIV, NO. 70. — JULY, 1857. 



11 



same, or a closely allied species, at a 

 5 lat. Vyb"" 13' N., long. 107^ 2' W., and 



kw^; 



