MESozoic. 265 
Presence of Reptilia Crocodilia Procoela ; Pythonomorj)ha 
Mosasaurus. Absence of Pisces Isospondyli Actinochiri ; Ptero- 
sauria Pteranodontidse ; Aves Odoutornithes. 
It remains to be seen whether these differences will remain 
under future investigation. 
FoxHiLLS. — Formed of sandstones more or less argillaceous, 
varying in thickness from thirty feet (Cope), Montana, to fifteen 
hundred feet (King), Colorado, to three thousand to thirty-five 
hundred feet in Southwest Wyoming (King). The vertebrate 
fauna in the West is sparse, but in New Jersey it is very full. It 
is characterized in Montana by 
Presence of Pisces Holocephali ; Ilaplomi (Ischyrhiza) ; Rep- 
tilia Pythonomorpha and Sauropterygia with short neck (Uro- 
nautes) ; Crocodilia Procoela. 
In JSTew Jersey it has the same characters, with the additions : 
Present : Pisces Percomorphi Berycidse ; Reptilia Testudinata 
Adocidfe and Pleurodira. Absent : Pisces Isospondyli Actino- 
chiri. 
Mr. King has combined the Benton, Niobrara, and Pierre into 
a single division', which he called the Colorado. On paleonto- 
logical grounds there is as yet no more reason for uniting these 
without than with the Foxhills group. If the Foxhills is 
retained as distinct, the others should be also. However, future 
research may change the present aspect of the case. 
Total thickness of the Cretacic of the West, about four thou- 
sand nine hundred feet. 
POSTCRETACIC SYSTEM. 
This name was proposed by Endlich and adopted and after- 
wards abandoned by White for the lacustrine formations which 
rest conformably on the upper beds of the Cretacic (Foxhills), 
whose paleontology will not permit them to be ranged with the 
Cenozoic system. The Vertebrata are as follows : 
Presence of Pisces Ginglymodi and Halecomorphi ; Reptilia 
Choristodera ; Mammalia Marsupialia Multituberculata. Absence 
of Pisces Isospondyli Saurodontidse and Actinochiri ; of Reptilia 
Sauropterygia and Pterosauria. 
There are two well-marked epochs of the Postcretacic, — the 
Puerco and the Laramie. 
Laramie. — Present : Pisces Elasmobranchi *Myledaphus ; 
