1878. | United States Survey of the Territories. 105 
ticular attention. The extensive explorations of Dr. Hayden in 
former years, and the paleontological investigations of the late 
Mr. Meek, pointed strongly to the equivalency of the Fort Union 
beds of the Upper Missouri river with the lignitic formation as it 
exists along the base of the Rocky mountains in Colorado, and ~ 
also to the equivalency of the latter with the Bitter Creek series 
west of the Rocky mountains. The investigations of this year 
have fully confirmed these views by the discovery not merely of 
one or two doubtful species common to the strata of each of 
these regions, but by an identical molluscan fauna ranging through 
the whole series in each of the regions named. 
This shows that the strata just referred to all belong to one 
well-marked period of geological time, to the strata of which Mr. 
King has applied the name of “ Laramie group” (Point of Rocks 
group of Powell). His investigations also show that the strata, 
which in former reports by himself and Professor Powell have 
been referred to the base of the Wasatch group, also belong to 
the Laramie group and not to the Wasatch. He has reached this 
later conclusion not merely because there is a similarity of type 
in the fossils obtained from the various strata of the Laramie 
group with those that were before in question, but by the specific 
identity of many fossils that range from the base of the Laramie 
group up into and through the strata that were formerly referred 
to the base of the Wasatch. Furthermore, some of these species 
are found in the Laramie strata on both sides of the Rocky 
_ mountains, Thus the vertical range of some of these species is 
no less than three thousand feet, and their present known geo- 
graphical range more than a thousand miles. 
Besides the recognition of the unity of the widely-distributed 
_ members of the formation of this great geological period, bounded 
_ by those of undoubted Cretaceous age below and those of equally 
_ undoubted Tertiary age above, his further observations: have left 
2 comparatively little doubt that the “ Lake Beds” of Dr. Hayden, 
as seen in Middle Park, the “ Brown’s Park group” of Professor 
= Powell, and the “Uintah group” of Mr. King, all belong to one 
and the same epoch, later than and distinctly separate from the 
_ Bridger group. 
In that portion of the region which lies adjacent to the southern 
base of the Uintah Mountain range, and which is traversed by 
Lake fork and the Du Chesne river, not only the Uintah group, 
ee ee aw ee ee 
