29 



" The occurrence of [I'os.sils specified] at the Jiiditii River localities would 

 certainly strongly favor the conclusion, not only that this Judith I'onnation, 

 the age of which has so long been in doubt, is also Cretaceons, but liiat even 

 the higher tVesii-water Lignite formation at Fort Clark and other Upper Mis- 

 souri localities may also be Upper Cretaceous instead of Lower Tertiary. 

 That the Judith River beds may be Cretaceous I am, in the light of all now 

 known oi" this rosion of the continent, rather inclined to believe. But it 

 would take very strong evidence to convince me that tiie higher Iresh-water 

 Lignite series of the Upper Mis.souri is more ancient than the Lower Eocene. 

 'J'hat they are not is certainly strongly indicated not only by the modern 

 afKnities of their molluscan remains, but also by the state of preservation 

 of the latter." 



I presume it is now apimrent that the presence of the orders Sauropte- 

 rygia and Dinosauria establishes, conclusively, the Mesozoic and Cretaceous 

 character of this fauna. This reference was made by the writer in 1869, 

 and was, at that time, opposed to the views extant, both geological and pale- 

 ontological. The following list exhibits the state of opinion on tliis point at 

 that time and subsequently. 



1856. Meek and Hayden, Proceedings of the Academy, Philadelphia, p. 63 ; 



referred them to the Tertiary. 

 Meek and Hayden, /. c, p. 265 ; Lignite, referred to the Miocene. 

 Meek and Hayden, /. c, 113 ; referred to Lower Tertiary. 

 Leidy, I. c, p. 312 ; Thcspesius oocidentaUs {Hadrosaurus) ; referred to 



the 3{am?nrJia, and regarded as dinosaurian. 

 Leidy, I. c, p. 89 ; Ischyrosaurus referred to the Mammcdia as a 



sirenian. 

 1860. Hayden, Transactions of the American Philosophical Society, p. 123; 



repeats former conclusions; Leidy refers llienpesius more decidedly 



to the Sauria, and questions relations of Ischyi'osaurus. 

 1868. Hayden, American Journal of Science and Arts, p. 204; Lignites 



regartled as Tertiary, from both vegetable and animal remains, 



from the Missouri and the Laramie Plains. 

 Leconte, Exploration of the Smoky Hill Railroad Route, |). Go ; the 



Middle Colorado beds are "older tiian those of the Mis.souri or 



Great Lignite bed of llaydcn, which are prul)ai)ly Miocene," ttc. 



