434 GEOLOGICAL SUEVEY OF THE TERRITOEIES. 



1856. Meek and Hay den, loc. cit, 113 ; referred to Lower Tertiary. 



1856. Leidy, loc. cit., p. 312 ; TJiespesius occidentals, {Hmlrosaurus,) 

 referred to the Mamuialia aud regarded as perhaps Dinosaurian. 



1856. Leidy, loc. cit., 1856, p. 89; Ischyrosaurus referred to the Mamma- 

 lia as a Sirenian. 



1860. Hayden, Transac. American Philosoph. Society, repeats former 

 conclusions, aud Leidy refers TJiespesius more decidedly to the Scmria. 



1868. Haydeu, Amer. Journal Science Arts, 1868, p. 204; Lignites, re- 

 garded as Tertiary, from both vegetable aud animal remains from the 

 Missouri and the Laramie Plains. 



1868. Leconte, Exploration of the Smoky Hill E. E. Eoute, p. 65 ; the 

 Colorado beds are "older than those of the Missouri or Great Lignite 

 bed of Hayden, which are probably Miocene," &c. 



1869. Cope, Trans. Amer. Philos. Soc, pp. 40, 98, 243 ; supposed mam- 

 malian remaius proved to be reptilian, and tlie formation referred to the 

 Cretaceous. 



1871. Kewberry, in Hayden's Annual Eeport, pp. 95, 96 ; Lignite flora 

 regarded as Miocene. 



1874. Cope, loc. supra cit. ; Lignite of IsTortbern Colorado referred to 

 tlie same horizon. 



The Judith Eiverbeds may be noticed in this connection. They have 

 yielded but few vertebrate remains, namely, six species of Eeptilia. Four 

 of these are Dinosauria, and hence diagnostic of the Mesozoic age of the 

 formation. The presence of a species, Radrosaurus mirahilis, Leidy , closely 

 allied generically and specifically to a species {H. fouUcei) of Cretaceous 

 Nos. 4 and 5 of New Jersey, induces me to believe that the formation is 

 Cretaceous, and such would appear to have been the suspicion of Messrs. 

 Meek and Haydeu when they originally described the deposit and its in- 

 vertebrate fossils. Leidy suspected that the species ''indicate the exist- 

 ence of a a formation like that of the Wealden in Europe."* Meek and 

 Hayden f remarked, " We are inclined to think with Professor Leidy that 

 there ma}' be at the base of the Cretaceous system a fresh-water forma- 

 tion like the Wealden. Inasmuch, however, as there are some outliers 

 of fresh-water Tertiary in these lowlands, we would suggest that it is 

 barely possible these remains may belong to that epoch." From the 

 stand-point of the writer, these beds would be at the top of the Creta- 

 ceous, and more or less related to the Fort Union epoch. Mr. Meek ex- 

 presses himself J cautiously with reference to the age of the Fort Union 

 and Judith Eiver formations, as follows: "The occurrence of" fossils 

 specified "at the Judith Eiver localities would certainly strongly favor 

 the conclusion not only that this Judith formation, the age of which has 

 so long been in doubt, is also Cretaceous, but that even the higher fresh- 

 water Lignite formation at Fort Clark and other Upper Missouri locali- 

 ties may also be Upper Cretaceous instead of Lower Tertiary. That the 

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

 known of this region of the continent, rather inclined to believe. But 

 it would take very strong evidence to convince me that the higher fresh- 

 water Lignite series of the Upper Missouri is more ancient than the 

 Lower Eocene. That they are not is certainly strongly indicated not 

 only by the modern affinities of their molluscan remains, but also by the 

 state of preservation of the latter," «&c. It is thus evident that the 

 paleontologists as well as stratigraphers have continued to regard the 



* Proceedings Academy Philadelj)hia, 1856, p. 73. 



t Loc. cit., 1856, p. 114. 



t Hayden's Annual Report, 1872, p. 450. 



