
CRETACEOUS AND TERTIARY—MILK RIVER. 119 
materially in thickness at the several localities where they were 
examined. They are slightly ferruginous, with prevailing light 
yellow tints, and are often more or less affected by false-bedding. 
Below the sandstones occur clays, sands, and arenaceous clays, generally 
well stratified, and individual beds of which may often be traced a long 
way up or down the valley. The colours are usually light, but there 
are some zones of darker carbonaceous clays, and in a few places impure 
lignites of no great thickness were observed. These appeared to be less 
persistent than most of the other beds, and generally to thin out and 
disappear when followed far in either direction. From their appearance, 
and mode of occurrence, these lignites may well have originated from 
the drifting together of wood or peaty matter, and differ considerably 
from the pure and definite beds which characterize the Lignite Tertiary 
further east, and which appear to be formed of trees which have grown 
on the spot. 
292. Above the sandstone zone is a great thickness of sands and 
arenaceous clays, forming more massive beds, in which the stratifi- 
cation is less perfectly marked. The general tints are pale greenish- 
grey, greyish, and light buff, 
293. No fossils were found in this upper series or in the sandstones. 
In the beds below the sandstones organic remains are also singularly 
rare, but are not altogether absent. In a part of the section not far 
below the base of the sandstone zone, is a layer with large arenaceous 
concretions, which contain in some places abundance of fossils. 
Among these are Melania Nebrascensis, one or more species of 
Paludina, a Helix, several species of Corbula, and a Spherium, which is 
almost certainly S. formosum, described by Meek and Hayden, from the 
Fort Union beds, and is identical with one afterwards found 110 miles 
further west, and within thirty miles of the base of the Rocky 
Mountains. A few rolled fragments of bone are also included in the bed, 
and some traces of fossil plants. Lower down in the section valves of 
Ostrea are found, sparingly scattered through the deposit, and not very 
far from the base a layer containing shells of Unio in a poor state of 
preservation was observed. Near the latter were found fragments of 
the bones of alarge vertebrate. They were scattered, and not in a very 
good state of preservation, and had evidently been strewn about after the 
death of the animal, and before their envelopment by the sediment. 
These, with the other vertebrate remains, were submitted to Prof. Cope, 

