652 THE ANCIENT LAKES OF WESTERN AMEBICA : 
he has published of these fossils, forms a contribution to 
paleontology not second in value or interest to that made by 
Cuvier in his illustrations of the fossils from the Paris basin ; 
nor to that of Faleoner and Cautley, descriptive of the fos- 
sils of the Sewalik hills of India. 
The scarcely less voluminous and interesting collections of 
fossil plants made by Dr. Hayden have been placed in my 
hands for my examination. Of these, the first instalments 
were described and drawn some years since as a contribution 
to the report of Colonel W. F. Reynolds, U.S.A., a report 
not yet published by the Government. The descriptions, 
however, were printed in the Annals of the Lyceum of Nat- 
ural History of New York, vol. ix, 1868. 
The general conclusions drawn from a study of this por- 
tion of Dr. Hayden's collections as regards the floras of the 
Tertiary and Cretaceous periods, the topography and climate 
of the interior of the continent, form a part of my contribu- 
tion to Colonel Reynolds’ report. Since that report was 
written, however, very large additions have been made to 
our knowledge of our later extinct floras, by collections of 
fossil plants made in different portions of the western part 
of our continent by Dr. Hayden, Mr. Condon, Dr. Le Conte 
and myself; and also by the collections made by Mr. W. H. 
Dall and Captain Howard in Alaska, and by several explor- 
ers on the continent of Greenland. 
Deferring for the present a comparison of the plants de- 
rived from strata of similar age in these widely separated 
localities, and the inferences deducible from them as regards 
the physical geography of our continent, I will say that the 
flora and fauna of the lake deposits on both sides of the. 
Rocky Mountains apparently belong to one and the same 
geological age, and tell the same story in regard to the to- 
pography, climate, conditions and development of animal 
and vegetable life. There is this striking difference, how- 
ever, perceptible at the first glance between the fresh-water 
Tertiaries of the east and west. In Oregon, Idaho and 
