966 The American Naturalist. [November, 
WIND RIVER AND BRIDGER BEDS IN THE 
HUERFANO LAKE BASIN: 
By Henry FAIRFIELD OSBORN. 
In 1888 Professor R. C. Hills, of Denver, announced his very 
important discovery of tertiary beds in the Huerfano River 
basin of southern Colorado. He contributed three papers to 
this subject in the Proceedings of the Colorado Scientific Society 
in 1888, 1889 and 1891, and finally divided the beds into three 
series, namely: 
; Huerfano Bed Bridger Group ..-.++++-s+.sseeseeerees 3,300. 
Huerfano Series Cachara Bod 
(Eocene) T sea lis ower Eocene Asie aa River 
| Poison Canon Beds ) Wasatch and Pu 3,500 
The identification of the Huerfano Beds proper was made by 
means of a large collection of fragmentary fossils. The iden- 
tification of the lower beds was upon stratigraphic evidence 
only, Professor Hill observing that they underlay conformably 
the upper beds. The essential features of his conclusions were 
as follows: 
(1) That the Huerfano series of 3,300 feet are equivalent to 
the Bridger or middle eocene, and the Cuchara and Poison 
Cafion series are probably equivalent to the lower eocene. 
(2) At the close of the Laramie period a great anticlinal 
axis arose to the east and southeast of the Wet Mountain 
Range and east of Spanish Peaks, forming the eastern border 
of the lake, extending fifty miles north and south, and from 
ten to twenty miles east and west. 
(3) The eruption of the laccolithie Silver Mountain and 
Spanish Peaks was subsequent to the Upper Lake Deposits of 
Bridger age. Hence these deposits are found upon the slopes 
of Spanish Peaks. 
(4) The drainage of the Huerfano Lake was to the north 
through the Wet Mountain Valley. 
‘Read before the American Association for the Advancement of Science at 
Detroit. 
