266 REPORT OF THE AMERICAN COMMITTEE. 
Reptilia Dinosauria Goniopodaand Orthopoda. Absent: Mam- 
malia Placentialia. 
This formation has an immense extent on the northern plains 
in the United States and Canada; along the eastern flank of 
the Rocky Mountains, and on the western flanks of the same in 
New Mexico, and along the Lower Rio Grande in Texas and 
Tamaulipas. It consists of sandstones, marls, and lignite, whose 
base rests conformably on the Foxhills beds of the Cretacic, when 
the latter is present. Thickness : 
Feet. 
East flank of Rocky Mountains, Colorado (King), . 1500 
Southwestern Wyoming (King), 5000 
Upper Missouri, Montana (Cope), .... 500 
Nortlivvestern New Mexico (Baldwin and Cope), . . 2000 
It is stated by White,* and agreed to by Ward and Newberry, 
that there are two epochs included under the name Laramie. 
This upper division, which has the greatest geographical extent, 
was named long ago by Hayden the Fort Union division. The 
other and lower or older division is the Bearriver of Hayden. 
The molluscan species of the two horizons are very different. 
The Bearriver beds are seen near Evanston, Wyoming, and in 
perhaps one or two other localities only. 
A formation has been observed along the Belly River, in Sas- 
katchewan, by the geological survey of the Dominion of Canada, 
which they call the Bellyriver. It is overlaid by the Pierre, 
and would be placed in the system in accordance with this position 
between that formation and the Niobrara below it. But the flora 
and the fauna, vertebrate and invertebrate, are identical, or nearly 
so, with that of the Laramie. The explanation of this singular 
state of the evidence has not yet been reached. 
PlTERCO. — Present: Mammalia Placentialia. Absent: Pisces 
Elasmobranchi ; Reptilia Dinosauria Goniopoda and Orthopoda. 
The fauna of this horizon is well distinguished from that of 
the Laramie in the absence of the numerous Dinosauria of the 
latter, and the presence of numerous placental mammalia in the 
former. On these grounds I at first referred the formation to 
* I do not claim two epochs for the Laramie proper, as I believe Ward does. 
I show that the '' Bearriver Laramie" fauna is entirely different from that of 
the Laramie proper ; but I don't know which is the older, or if either is. No 
plants have been found in the Bearriver Laramie^ C. A. W. 
