28 TERTEBEATA OF THE TERTIARY. 



appeared, accompanied by the peculiar form Erisichthe, and the family of 

 StratodontidfB. The genera of Mount Lebanon, Leptotrachehts and Spanio- 

 don, occur in this bed in Dakota ; but the closest parallelism is exhibited 

 with the Lower Chalk or Turonian of Western Europe. The general fades 

 of the reptilian fauna is that of the Lower Chalk, and there is little doubt 

 that several genera are identical in the two continents, e. g. Elasmosauru^. 

 The apparent peculiarity of the Chalk in America is the abundance of 

 forms (four genera) of Fi/lhonomorpha, with numerous species, while but two 

 genera have yet been found in Europe, and the presence of birds with 

 biconcave vertebrae and teeth. This interesting type, which was first dis- 

 covered by Seeley in the genus named by him Enaliornis, and afterwards 

 found by Marsh to possess teeth, has been found at a lower horizon in 

 England, the Upper Greensand. But in England, France, and Westphalia 

 occur the genera of fishes above mentioned, as Portheus, Ichthyodectes, Saic- 

 rodon, Saurocephalus, Erisichthe, Empo, Pachyrhizodus, Enchodus, Leptotra- 

 chelus, etc. This close relationship of the horizons permits an identifica- 

 tion, and it is the first instance which appears to me to be susceptible of 

 satisfactory demonstration. 



The next horizon of the Cretaceous which has yielded many verte- 

 brate remains in North America is the Fox Hills formation (including the 

 Fort Pierre bed). Here the genus Mosasaurus appears in America, and is 

 accompanied by the earliest crocodiles with procoelous vertebrae, and by 

 numerous marine turtles which partake of the characters of both CMydri- 

 d(B and Cheloniida, which I have called the Propleuridce. Beryx appears first 

 here in America. The predominant genus of fishes is Enchodus, and the 

 principal Dinosauna are Lcdaps and Hadrosaurus. This horizon has been 

 ])arallelized with the Maestricht of Europe, and several genera are common 

 to the two beds ; such are Mosasaiirus and Enchodus. The genus Hadro- 

 saurus, and the family of turtles I have called the Adocida, remain undis- 

 covered in Europe ; hence the identity of faunaj cannot be established. 



The lacustrine beds, or summit of the American Cretaceous series, the 

 Laramie of Hayden, present the remains of a populous fauna and a rich 

 flora. The students of the palneobotany have declared this flora to be of 

 Eocene, and the later portions of Miocene, character, while tlie lacustrine 



