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25, D. C. 



GEOLOGICAL SURVEY OF CANADA 



1.— DISTINCTIVE CHARACTERS OF THE MID-CRETACEOUS FAUNA. 



By Henry Fairfield Osborn 



The determination by the Canadian Survey of a Mid-Cretaceous and fresh-water 

 fauna, including iishes, batrachians, reptiles and naammals, is a forward step of great 

 importance in vertebrate palaeontology. 



The Survey had established beyond question, geologically, that the Belly River series 

 is Mid-Cretaceous, that it underlies the Montana or Ft. Pierre-Fox Hills group, and over- 

 lies the Ft. Benton and Dakota groups ; =^ and at the outset of the palceontological investi- 

 gations for this report, the question arose, what stages of vertebrate evolution are repre- 

 sented by the Belly River fauna ? 



It soon appeared to the writer in the study of the fine collection made by Mr. Lambe 

 that the Belly River vertebrates of the North-west' Territory were of decidedly different 

 and apparently of older type than those from the Laramie beds of Converse co., Wyoming, 

 described by Marsh, and were rather to be compared with those described by Leidy, 

 Cope and Marsh, from Montana, chiefly from the Judith River beds, a region by no 

 means distant geographically. 



Thus the correlation between the Belly River and Judith River series, proposed by 

 the late Director, Dr. Gr. M. Dawson, in 1815, at first glance appeared to be confirmed 

 faunistically. But this correlation is not supported by the geological records, which all 

 plac4 the Judith River beds proper above the Fox Hills and Fort Pierre. 



To present the evidence for and against the Mid-Cretaceous age of some of the 

 Montana fossils already known, to show the need of closer examination of the geology 

 and closer comparison of types, and to outline the general characteristics of this fauna, 

 are the chief objects of this introduction. No7i s;eologia sine palaontologia ; in other words, 

 no faunal work will endure which is not based on stratigraphical work. 



1. G-EOLOGicAL Relations. 



Among geologists of the United States there has never been any question as to the 

 Laramie or Upper Cretaceous age of the typical Judith River beds. In 1877, Cope 

 referred the Judith River formation of Meek and Hayden to the Cretaceous. In 1887, he 



' The history of this work is presented by Mr. Lambe in the second part of this memoir. 



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