White and Cope—The Green River Group. 413 
buttes in this region, but the fissile shales were found only on 
Sentinel Butte. It is probable, however, that they will be 
found at the top of other buttes in that region. 
Searching these shales I found the two species of fishes 
which are described in following paragraphs by Professor Cope, 
but no other traces of fossils of any kind were discovered in 
them. It will be seen from Professor Cope’s remarks that. 
these fishes are not closely related to any hitherto described, 
and they are therefore not of service in directly identifying the 
strata from which they come with the Green River Group or 
With any other. They are, however, of such a character that 
they may have lived in such lacustrine waters as the Green 
River Group was deposited in. 
In the absence of paleontological evidence we must rely upon 
the stratigraphical relations of this deposit in considering its 
claim to be regarded as a part of the Green River Group. 
am by no means confident that this small deposit is a part of 
that group, and once continuous with the same to the south- 
westward; or that it is in any sense equivalent with the 
same; but the following facts are worth considering in that 
connection. 
(1.) This small fish-bearing deposit follows in regular order, 
and rests conformably upon certain sandstone strata, which in 
turn rest conformably upon typical Laramie strata. The Green 
River Group at its typical localities in like manner rests con- 
_ formably upon the Wahsatch Group which in turn rests (in 
many places at least) conformably upon the Laramie Group. 
(2.) The lithological characteristics of this fish-bearing de- 
posit are surprisingly like the fish-bearing layers of the Green 
River Group. 
(8.) Although the fishes of this deposit are not identical with 
any known forms in the Green River Group, their characteris- 
ties are such that. no reason is apparent why they may not have 
lived at the same time and in similar, if not the same, waters 
as those that have been discovered in that group. 
(4.) Their nearest affinities are with fishes that have been 
found in the Green River Group, and none like them have ever 
en found in the Laramie Group. 
It may be objected that in the Green River region the great 
Wahsatch Group exists between the Green River and Laramie 
roups; and that it has not been shown to be present in con- 
hection with the small fish-bearing deposit in question. In re- 
ply it may be remarked that although so thin, the coarse sand- 
Stones between this small fish-bearing deposit and the Laramie 
Strata on Sentinel Butte may be reasonably Tae to repre- 
sent both the Lower Green River Group of Powell and the 
Wahsatch Group of Hayden. Indeed it seems plausible that 
