THE 
AMERICAN GEOLOGIST. 
VOL. XXXV. JUNE, 1905. No 6. 
THE FOSSIL TURTLES OF THE BRIDGER BASIN. 
By O. P. Hat, New York. 
The greater portion of the deposits known as the 
Bridger beds lie in the Bridger basin, a tract extending 
northward from the Uinta mountains to about latitude 42°, 
and east of the Wasatch range from about longitude 110°, 
30 min., to about 109°, 30 min. The north and south ex- 
tent of the basin is therefore about fifty miles, the east and 
west extent about sixty miles. The thickness of the de- 
posits is given as from 2000 to 2500 feet. The strata are 
composed of clays, more or less arenaceous, interrupted 
beds of sandstone, and occasional thin layers of limestone. 
The argillaceous beds are usually yellowish, grayish, or 
greenish. The sandstc/ne masses are commonly rusty 
brown. The stratification has a dip of from two to four 
degrees to the north. 
Hitherto geologists have regarded these beds as lake 
deposits. Cope, Powell. Emmons, and King considered 
them to be such. There are large portions of this basin 
which the writer has not seen ; but in 1903 he spent nearly 
two months in such typical portions of it as the Grizzly 
buttes and the region about the mouth of the Cottonw^ood 
creek. From oJ)servations made there the conclusion was 
reached that the deposits had been made almost wholly 
through river action. It is difificult to comprehend how 
such coarse materials as are often found in even the finer 
clay deposits could have been borne far out into the bed 
of a lake. Had the deposits been made in a lake there 
ought to be found, at each level, extensive tracts of very fine 
materials, representing the quiet central portions of the 
