132 GEOLOGY AND PALEONTOLOGY. 



The specimens collected by Lieutenant Abert,* at Poblazon, are doubtless of this species, and 

 are referred by Professor Bailey to the same species as those of Fremont's report. The same 

 species was brought by Captain Stansbury f from between the Big and Little Blue rivers, in 

 precisely the same conditions, and in a similar rock. In 1854 I received specimens of the same 

 fossil, collected at several points on the Arkansas, by Colonel Fremont, during his later expe- 

 dition. These occur in part in a bluish, or dull lead-colored, argillaceous limestone, and others 

 in a gray or buff-colored limestone. 



Dr. Schiell collected this species of Inoceramus at the bend of the Arkansas river ; and it is 

 mentioned by Dr. Roemer as occurring near New Braunfels, in Texas. Dr. F. V. Hayden has, 

 more recently, brought the same from the bed No. '3, Nebraska. 



In Arkansas, this fossil is collected from the same localities, and apparently in the same 

 position from which are obtained numerous species of Echinoderms, Gryphcea Pitcheri, and other 

 fossils of species yet unknown in Nebraska, or in any localities east of the Mississippi river. 



Fragments of the same species of Inoceramus occur in an argillaceous limestone, among the 

 collections of the Boundary Survey, from the basin of the Rio Grande. In the same connexion 

 occur several Echinoderms of species identical with those from Arkansas — Gryphcea Pitcheri, 

 Ammonites Texanus, etc. 



The collections of the Pacific Railroad Surveys, which have been placed in my hands for 

 examination, show that Ostrea congesta was collected by Mr. Marcou, from a point three miles 

 north of Galisteo, between Fort Smith and Santa Fe.l This fossil, in Nebraska, is associated 

 with Inoceramus prohlematicus. In the same collection, and from the same locality, near 

 Galisteo, there were specimens of a slaty limestone containing fragments of Inoceramus, which, 

 although not identified at the time, is probably the Inoceramus prohlematicus. Thus we have 

 abundant evidence of the distribution of tliis species from Nebraska to New Mexico. 



The section already established for the cretaceous strata upon the Missouri, as given above, 

 and the occurrence oi Inoceramus prohlematicus in the beds Nos. 2 and 3 of that section^ serve to 

 fix the place of that fossil in the series in reference to the other beds constituting the cretaceous 

 formation in Nebraska. From the analogy of the beds Nos. 4 and 5, and the identity of several 

 important species of fossils with those of New Jersey, Alabama, and Tennessee, we may regard 

 the position of this fossil as determined in reference to the members of the series which occur in 

 these States, this species having never been found, so far as we are aware, in either New Jersey, 

 Alabama,, or Tennessee. Thus this fossil becomes one of the best guides for the identification 

 of certain strata in the cretaceous system of the United States. 



In a paper recently published in the proceedings of the Academy of Natural Sciences, by 

 Messrs. Meek and Hayden, speaking of the geographical distribution of the cretaceous fossils, 

 they refer to the well known species Ammonites placenta, Scaphites Conradi, Baculites ovatiis, 

 and Nautilus Dekayi, as being common to the central or upper portions of 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, they remark : 



" At the same time the total absence of the above named fossils, and, indeed, so far as we yet 



« Report on a Geograghical Examination of New Mexico, by Lieutenant J. W. Abert, 1848. Notes concerning the min- 

 erals and fossils, by Professor J. W. Bailey, page 547. See note [pp. 117, 118] of the present report. 



f Exploration of the Valley of the Great Salt Lake, by Captain Howard Stansbury, 1852. Appendix, geology and paleeon- 

 tology, by James Hall ; page 402. 



% See Pacific Railroad Reports ; survey of the thirty-second parallel ; Chapter IX, page 102. 



