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MEMOIR OF EDWARD D. COPE. 405 
because of the lack of fossils common to them and other localities, and 
the absence of decisive stratigraphical evidence, he was inclined to con- 
sider them as being of late Kocene or more probably Oligocene age. 
Although Cope immensely increased our knowledge of the vertebrate 
fauna of the John Day stage and dealt in a masterly way with the abun- 
dant fossils of that formation, yet he has little to say about its geology 
beyond what had already been determined by previous observers. In 
the Loup Fork, on the other hand, his observations were fairly revolu- 
tionary. The Loup Fork fauna was first described by Leidy, who referred 
it tothe Pliocene. This determination was a natural one, for Leidy’s ma- 
terial had been for the most part hastily picked from the surface of the 
ground and contained many specimens which had been weathered out 
from overlying Pleistocene deposits. Thisadmixture of Pleistocene spe- 
cies gave to the fauna a very modern character, while at the same time 
it contained too many extinct and peculiar genera to be referable as a 
whole to the Pleistocene. Its determination as Pliocene was thus ina 
measure inevitable; but Cope was from the first suspicious of the refer- 
ence, and he therefore made his collections in areas where the Loup Fork 
beds were at the surface and where no newer overlying strata could fal- 
sify the faunal lists. ‘This enabled him accurately to determine the ele- 
ments of which the Loup Fork fauna really consisted, and to eliminate 
the Pleistocene forms which had been mistakenly included in it. Having 
accomplished this, he came at once to the conclusion that the Loup Fork 
beds were not Pliocene at all, but upper Miocene. Though this deter- 
mination is unquestionably right, and although it was a great reform in 
western stratigraphy, several American geologists have refused to adopt 
it, but have continued to uphold Leidy’s original reference. Their ex- 
ample has led many European writers astray and with very unfortunate 
results, vitiating much careful and otherwise excellent work. Cope’s 
observations also greatly extended the known area of the Loup Fork 
beds, determining their presence in New Mexico and Texas and in the 
valley of Mexico. 
The foregoing does not exhaust Cope’s important contributions to the 
geology of the Loup Fork, for he was the first to show that that forma- 
tion is divisible into distinctly marked substages. In 1875 Grinnell and 
Dana discovered certain lacustrine deposits in the valley of Smith river, 
central Montana, which they determined as Pliocene, by that term prob- 
ably meaning Loup Fork. Cope subsequently sent a collector into this 
region, and from the material thus gathered he made a highly important 
determination. He showed that these beds constituted a separate sub- 
stage of the Loup Fork, and that they were older than any part of that 
formation which had been known up to that time. As helping to bridge 
