268 [November, 



the beds No. 2 and 3 of our section. This conclusion is further strengthened 

 by the fact that the only Nebraska species yet found in the south west, so far 

 as we know, are Inoceramus problematicus and Osirea congesta, both of which are 

 unknown in the north west excepting in the above named beds, and are mainly 

 restricted to the latter. The well marked specific characters ofthese two fossils, 

 and their limited vertical range, together with their extensive geographical 

 distribution, render the bed in which they occur a horizon of the highest 

 importance in the identification of strata at remotely separated localities in these 

 far western territories. 



That these beds, or formations of the same age, are widely distributed over a 

 vast area of country, extending from near the great bend of the Missouri in lat. 

 44 15'', long. 99 20'', westward to, and perhaps beyond, the eastern slope of 

 the Rocky mountains, and far south into Texas and New Mexico, is highly pro- 

 bable, from the occurrence of their characteristic fossils at many widely separated 

 localities in this region. At any rate, we know, from information obtained 

 through Mr. Henry Pratten, of the Geological Survey of Illinois, i\i&i Inoceramus 

 problematicus is found in a light colored limestone overlying a red sand stone on 

 Little Blue river, a tributary of Kansas River. Col.' Fremont also collect- 

 ed specimens of the same shell from a similar rock on Smoky Hill river, in lat. 

 39, long. 98, and at other localities between there and the Rocky mountains.* 

 More recently, Lieut. Abert found the same, or a closely allied species, at a point 

 as far south west as lat. 35 13' N., long. 107 2' W., and apparently on the 

 western declivity of the anticlinal axis of the Rocky mountains.f Roemer like- 

 wise collected in Texas specimens of a shell he refers to Inoceramus myteloides of 

 Mantell, which is considered identical with /. problematicus of Schlotheim. In 

 addition to this, we have seen, in Mr. Marcou's collection, specimens of Osirea 

 congesia, from Galisteo, between Fort Smith and Santa Fe, where it probably 

 holds the same geological position as the so-called Gryphcea dilatata. 



The formations from which the above named fossils were obtained Jn the 

 south western Territories, appear, from the statements of the various explorers 

 of that region, to repose on a series of red, yellow, and whitish sandstones and 

 various colored clays, which are referred by Mr. Marcou to the Jurassic and 

 Triassic systems. These lower beds we think are represented wholly, or in 

 part in Nebraska, by our formation No. 1, which, as previously stated, we re- 

 gard as probably belonging to the lower part of the Cretaceous system, though 

 it may be older. 



In the remarks accompanying our paper on the fossils of the Lignite Tertiary 

 formations of Nebraska, although satisfied they must be middle or lower Tertiary 

 types, we refrained from the expression of any opinion as to the exact age of 

 the beds in which they were found ; not having been able to identify positive- 

 ly any of the species with characteristic forms of either of these members of the 

 Tertiary system in other countries. Being all specifically distinct from previously 

 known forms, and belonging nearly exclusively to land and fresh water genera, 

 we could of course base no conclusions on comparisons with the fossils of the 

 Tertiary formations hitherto most successfully investigated on other parts of 

 this continent, since the latter deposits are almost wholly characterized by 

 marine genera. So far as we had been able to compare them with figures and 

 descriptions of foreign species, the evidence appeared contradictory, some of 

 them being like Miocene and others like Eocene types. As we now have, how- 

 ever, the additional weight of evidence derived from Dr. Newberry's investi- 

 gations of the fossil flora of these formations, in favor of the conclusion that they 

 are of Miocene age, we can no longer hesitate in referring them to that epoch. 

 Dr. Newberry's opinion on this point is worthy of the highest confidence, since, 

 in addition to an extensive and accurate general knowledge of fossil botany, 

 he has had the advantage of being able to make direct comparisons of these 

 plants with the flora of well determined Miocene deposits in California. 



* See Prof. Hall's figures and remarks in Fremont's report, p. 174, pi. 4. 



f Lieut. Abert's report of explorations in New Mexico and California, p. 547. 



