MESOZOIC. 29 



constitution of the strata has influenced the stratigraphic geologists to con- 

 cur in the view that the formation should be arranged with the Tertiary 

 epochs. That the fauna was of a mixed character is the result of a study 

 of its vertebrate fossils. The predominant type in North America was the 

 Dinosauria, which were abundant in species and individuals, and this fact 

 alone will suffice most paleontologists as a reason for referring the epoch 

 to the Cretaceous series. The genera of Dinosauria (Palcsoscincm, Ciono- 

 don, Diclonius, Monocloniiis, Bysganus, etc) have not yet been found in any 

 other part of the world. Mingled with them were species of crocodiles 

 and turtles of indifferent character, while a number of other forms existed 

 which had a limited range in time, and hence are important indicators of 

 stratigraphic position. Such are the genera of fishes, MyledaijJius Cope and 

 Clastes Cope, which have been found also near Reims, France, by Dr. 

 Lemoine, in the Sables de Bracheux, which are regarded as the lowest Ter- 

 tiary. Such is the curious Saurian type Champsosaurus (Cope) {Simcedo- 

 saurus Gerv.), and the turtle genus Compseniys Leidy, which Lemoine finds 

 a little higher up in the series, in the conglomerate of Cerny, which is in 

 the lower part of the Suessonian. In France, a genus of the Laramie, 

 Polythorax, extends into the Lignite or Upper Gorypliodon bed of the Sues- 

 sonian Thus the Laramie is intercalated by its characters between the 

 Cretaceous period on the one hand and the Tertiary on the other, and its 

 fauna includes genera and orders of both great series. These relations may 

 be exhibited in tabular form as follows. I here include the faunae of the 

 Sables de Bracheux and of the conglomerate of Cerny as one, since both 

 possess the types of the Laramie, while the horizon of the Lignite of 

 Meudon, or the Suessonian, does not. 



Sables de Bracheux and Con- Laramie. 



GLOMERAT DE CeRNY. 



a. Teetiaey. 



Lophiochosrus. 



Plesiadapis. 



Pleuraspidotherium. 



Arctocyon. 



Clastes. Clastes. 



