162 The America II Geologist. September, 1895 
of the Mesjibi rc<i,'i()n :i re derived. Altlioujjjh as yet no identi- 
tiable organic t'orins have ])een detected in the few microscopic 
slides that have been made, their i)resence in the rock origi- 
nally^ is so strongly indicated by all the attendant circum- 
stances that Mr. Spurr has included it as probable amongst 
his final conclusions.* This disc(»very is also in line with the 
late announcement by Mr. W. I). Matthew of the discovery of 
many foraminiferal forms associated with a large amount of 
iron in the St. John group, in New Brunswick,! which i)oints 
to the Lower C'ambrian age of the upper iron-bearing rocks of 
the Mesabi region. 
THE MENTOR BEDS: 
A CENTRAL KANSAS TERRANE OF THE COM- 
ANCHE SERIES. 
By F. W. ("ragin, Colorado Springs, Colo. 
The Mentor bads, named from a small station in Saline 
county, Kansas, within the area of their outcrop, are a terrane 
of variegated, earthy-textured marine shales, with interca- 
lated beds of brown sandstone, resting in part conformably 
upon the Kiowa shales and in part unconformably upon the 
drab and purple-red laminated shales and impure limestones 
of the Permian, and succeeded above by the more heavily are- 
naceous fresh-water sediments of the Dakota. They were 
formerly considered by all geologists as constituting a part of 
the Dakota group, but are now known to belong to the upper 
part of the Comanche series. 
The Mentor beds occur typically in Saline county, to whose 
area their outcrops contribute more than those of any other 
formation, and nearly all of that part over which the Dakota- 
sandstone-topped Iron Cap mound. North Pole mound. Soldier 
Cap mound, and Smoky Hill buttes stand sentinel and indi- 
cate the comparatively recent erosion of the Dakota. They 
occur in the southeastern quarter of Ellsworth county also, 
extending thence eastward across the northern part of Mc- 
Pherson county, to and beyond the noted double eminence, 
♦American Geologist, vol xiii, p. 335. 
Bulletin X, Minnesota Geological Svu-vey, 1894. 
tTrans. N. Y. Acad. Sci., vol. xii, pp. 108-120, 1893. 
