8 



1856. Leidy, 1. c, 1856,?p. 89; Ischyrosauriis referred to the Mammalia 

 as a Sirenian. 



1860. Hayden, Transac. American Philosopb. Society; repeats former 

 conclusions, and Leidy refers Thespesius more decidedly to the Sauria. 



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

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

 Missouri and the Laramie plains. 



1868. Leconte, Exploration of the Smoky Hill E. R. Route, 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, Traus. Amer. Philos. Soc, pp. 40, 9S, 243 ; supposed mam- 

 malian remains proven to be reptilian, and the formation referred to the 

 Cretaceous. 



1871. Newberry, in Hayden's Annual Report, pp. 95, 96 ; Lignite flora 

 regarded as Miocene. 



1874. Cope, loc. suj)ra cit.. Lignite of l!forthern Colorado referred to 

 the same horizon. 



The Judith River beds may be noticed in this connection. They have 

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

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

 formation. The presence of a species, Hadrosaurus miraMlis Leidy, closely 

 allied generically and specifically to a species fH.foulkeiJ 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 Hayden when they originally described the deposit and its in- 

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

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

 Haydent remarked, " We are inclined to think with Prof. Leidy that there 

 may be at the base of the Cretaceous system a fresh-water formation 

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

 freshwater Tertiary in these lowlands, we would suggest that it is 

 barely possible these remains may belong to that epoch." Prom 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* cautiously with reference to the age of the Fort Union 

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

 specified "at the Judith River 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 Riverbeds may be Cretaceous, I am, in thelight 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 thej'- are not is certainly strongly indicated not only by 

 the modern afSnities of their moUuscan remains, but also by the state ot 

 preservation of the latter," &c. It is thus evident that the paleontolo- 

 gists as well as strati graphers have continued to regard the Lignite 

 series as Eocene and not Cretaceous, as is and has been maintained by 

 the writer since 1868. 



VII. The Bitter Ceeek series, mentioned by the writer as a dis- 

 tinct group in the proceedings of the American Philosophical Society, 



'Proceedings Academy Philadelphia, 1856, p. 73. 



t L. c. 1856, p. 114. 



'Hayden's Annual Report, 1872, p. 450. 



