W. J. McGee—Drift Formations in Northeastern Iowa. 341 
metamorphic rocks from far to the northward. ‘These, hov 
ever, are quite abundant. In some fields it has been necessary 
however. Perhaps one in a thousand shows plainly grooves 
and deep scorings; but many others are less distinctly marked. 
Still not more than one-tenth exhibit any other marks of glacial 
action than a rounded form. 
The Forest Bed is found at many other localities in Iowa, 
and within it the bones of the mastodon and beds of peat 
have been discovered.+ The writer has also seen crania of 
Bison iatifrons from the same horizon. It has generally been 
considered to be—in other places as well as in Iowa—a post- 
must be of interglacial age; and from a recent examination 
the writer is convinced that the overlying deposits in Illinois 
the slow retreat of the glacier. In Nebraska this carbonaceous 
stratum has been found resting on glacial Drift and overlaid 
WM both the Drift of the later glacier and the Loess of the 
Missouri Valley.t The similarity of the organic remains found 
in this stratum wherever exposed indicates a like age for its 
deposits over the whole territory in which it 1s found. 
* Dr. 0. A. White’s Geol. Rep. (of Iowa), 1870, vol. i, p. 87. 
en c., pp. L17, 118, 119, and 339. : 
“Superficial Deposits of Nebraska;” from Hayden's Report for 1874, p. 5. 
Farley, Iowa, March 12th, 1878. 
M, JOUR, vomnedsones Series, Vou. XV, No. 89,—May, 1878. 
