FLORA OF THK LAEAMIE GROUP. HI 



vertebrates of Europe and North America^ contains very valuable and 

 interesting documents, which really show thnt the evidence afforded as to 

 the age of the Laramie Group both by the remains of animals and by those 

 of plants is not far discordant. In the table indicating the correlation of 

 fill the formations from the lowest to the more recent (pp. 50 and 51 of the 

 memoir quoted above) the hoi-izon of the Sezanne flora, or the Pisolitic 

 limestone, is not separately indicated, but is probably in what the author 

 calls the Puerco stage, hypothetically identified with the Thanetian, or 

 lower Eocene; the whole Puerco and Laramie on one side, and the Sables 

 of Bracheux on the other, being marked as Post-Cretaceous. Now the rela- 

 tion and difference between the vertebrates of the Laramie and those of 

 the Sables of Bracheux is established by Professor Cope as follows: "The 

 genera of Linosauria f Palceoscincus, Cionodon. Diclonms, Monoclonhis, 

 LysganusJ, which constitute a predominant type in the Laramie Group, 

 have not been found in any other part of the world. Mingled with them 

 were species of crocodiles and turtles of inditferent characters, wiiile a 

 number of other forms existed which had a limited range in time, and 

 hence are important indications of stratigraphic position. Such ai:e the 

 genera Myledaphus (Cope) and Clastes (Cope), which have been found also 

 near Rheims, France, by Dr. Lemoine. in the Sables de Bracheux. which 

 are regarded as the lowest Tertiary. Such is the curious Saurian type 

 Champsosaurus (Cope), Simcedosaurus (Grev.),and the turtle genus Comp- 

 ■semys (Leidy), which Lemoine finds a little higher up in the series in the 

 conglomerate of Gerny, which is the lower part of the Suessonian. In 

 France, a genus of the Laramie, Polytliorax, extends into the Lignite or 

 upper Coryphodon beds of the Suessonian. Thus the Laramie is inter- 

 calated in its characters between the Cretaceous period on one hand and 

 the Tertiary on the other, and its fauna includes genera and orders of 

 Jjoth great series." 



Admitting the exposition of the characters of the strata as made by 

 the celebrated author of the notice, it may be observed that, from the 

 table which follows the above remark, all the genera common to the Sables 

 of Bracheux and the Laramie Group forcibly indicate relationship to the 



'The relation Lif the horizon of extinct vertebrata of Europe and Norlli America. "U. S. Gcol. «& Geog. 

 ■Survey" (Ha.vden), Bull, v, No. 1. 



