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



I 



Little Blue Rivers, in precisely the same conditions and in a sim- 

 ilar rock. In 1854 I received specimens of the same fossil col- 

 lected at several points in Arkansas by Col. Fremont in his later 

 expedition: these occur in part in a bluish or dull ash-colored 

 argillaceous limestonCj and others in a gray or buff-colored 

 limestone. 



Dr. Schiell collected this species of Inoccramus at the bend of ' 

 the Arkansas River ; and it is mentioned by Dr. Roomer as oc- 

 ciirring near New Braunfels in Texas. Dr. F, V. Ilayden has 

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

 as just stated on a previous page. 



In Arkansas this fossil is collected from the same localities 

 and apparently in the same position from which are obtained 

 numerous species of Echinoderms, Gryphcjea 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 con- 

 nexion occur several Echinoderms of species identical Avith those 

 from Arkansas, Oryphcea Pitcheri^ Ammonites Texanus^ etc. 



The collections of the Pacific Railroad Surveys, w^hich have 

 been placed in my hands for examination, show that Ostrea con- 

 gesta was collected by Mr. Marco u from a point three miles north 

 of Galisteo; between Fort Smith and Santa Fe."^ 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 Ino- 

 ceramus, which, although not identified at the time, is probably 

 the Inoceramif^ prohlematicus. Thus we have abundant evidence 

 of the distribution of this species from Nebraska to New Mexico. 



The section already established for the cretaceous strata upon 

 the Missouri as given above, and the subsequent discovery by 

 Dr. Hayden of the occurrence of 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 of the section. 

 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 never having been found, so 

 far as we are aware in either New Jersey, Alabama or Tennessee. 

 This fossil thus becomes one of the best guides for the identifi- 

 cation of certain strata in the cretaceous system of the United 

 States. 



* See Pacific Railroad Reports, Survey of the 32ad parallel, Chapter IX. 



