32 The America?i Geologist. January, i90(» 
locality. The result of the investigation was a paper entitled 
"The Mentor Beds."* 
The Mentor beds are described by professor Cragin as, 
"\^ariegated, earthy textured, marine shale with intercalated 
beds of brown sandstone resting in part unconformably on the 
drab and purple-red laminated shales and impure limestones 
of the Permian and succeeded above by the more heavily 
arenaceous fresh water sediments of the Dakota. * ='•- * 
They weather into gentle slopes * * * and present few 
conspicuous outcrops." f 
Professor Cragin does not give any sections, and, accord- 
ing to professor Jones, did not at the time of writing the paper 
know of any outcrops containing fossils in situ. 
b. Stratigraphy. 
The stratigraphy of the Mentor beds is not easy to work 
out. The best and in fact the only typical exposure in the 
locality containing Mentor fossils in place, so far as known to 
the writer, is at a point one hundred yards southwest of the 
creamery at Brookville, eighteen miles southwest of Salina. 
Professor Jones found Mentor fossils in the bed of Spring- 
creek at the creamery and on September 29, 1898, Dr. T. W. 
Stanton discovered the fossils in a bank a short distance up 
the stream. They were found in concretion-like masses of 
dark brown to black sandstone varying from a few inches to 
two or three feet in length. These concretions lie in horizontal 
row^s in a ledge of soft grayish brown sandstone. The concre- 
tions weather out and roll down the slopes and form the bould- 
ers in which the fossils so far obtained are found. These con- 
cretions vary much in size. At places they are wanting alto- 
gether and again they are so large as to cause the appearance 
of ledges or even to form small escarpments. 
The following section was taken at the creamery at Brook- 
ville. The base is probably not to exceed fifty feet above the 
Permian. 
♦American Geologist, vol. XVI, pp. 162-165, 1895. 
tibid., p. 162. 
