No. 1.] 



COPE ON HOEIZONS OF EXTINCT VERTEBEATA. 



37 



flora. The students of tlie palseobotany have declared this flora to be 

 of Eocene, and the later portions of Miocene character, while the lacus- 

 trine constitution of the strata has influenced the stratigraphic geolo- 

 gists to concur 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 

 ]iSrorth America was the Dinosauria, which were abundant in species 

 and individuals, and this fact alone will suffice most palaeontologists as a 

 reason for referring the epoch to the Cretaceous series. The genera of 

 Dinosauria [Palceoscincus, Cionodon, Diclonius, Monoclonkis, Dysganus, 

 etc.) have not yet been found in any other part of the world. Mingled with 

 them were species of crocodiles and turtles of indifterent character, while 

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

 hence are important indicators of stratigraphic position. Such are the 

 genera of fishes, MyledapJms Cope and Clastes Cope, which have been 

 found also near Eeims, France, by Dr. Lemoine, in the Sables de Bra- 

 cheux, which are regarded as the lowest Tertiary. Such is the curious 

 Saurian type Cliampsosaurus (Cope) {Simwdosaurtis Gerv.), and the tur- 

 tle genus Gompsemys Leidy, which Lemoine finds a little higher up in 

 the series, in the Conglomerate of Cerny, w^hich is in the lower part of 

 the Suessonian. In France, a genus of the haxaimiej Poly thorax, extends 

 into the Lignite or upper CorypJiodon bed of the Suessonian. 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 ex- 

 hibited in tabular form as follows. I here include the faunse 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 Be-acheux and Con- 



GLOIVIERATE DE CeENY. 



Laeamie. 



a. TERTLARY. 



LopMoclicerus. 



Plesiodapis. 



Pleuraspidotherium. 



Arctocyon. 



Clastes. 



Clastes. 



Champsosaurus. 



Gompsemys. 



Myledaphus, 



/3. Peculiar. 



Champsosaurus. 

 Gompsemys. 

 Myledaplms. 

 Scaplierpeton. 



