216 University of Kansas Geological Survey. 
90 to 130 feet. The indications are that the group thins out toward 
the south. 
The Bituminous Shale Horizon.—The shales comprising this hori- 
_4on vary in thickness from 20 to 40 feet. They are dark blue in color 
and somewhat slaty in structure. Upon weathering they present 
a laminated appearance. In many places they extend upward to- 
ward the next horizon gradually changing color from blue to yellow. 
Very few fossils are found in this horizon, Inoceramus liabatus being 
the most abundant. 
The Lincoln Marble Horizon.—Resting conformably upon the bitu- 
minous shales is the Lincoln Marble horizon. This group consists 
of from two to five layers of hard flinty limestone intercalated with 
shales. The maximum thickness of the group is 15 feet. The maxi- 
mum thickness of the individual layers is 6 inches. The Lincoln 
Marble is of a bluish gray color, contains many impurities, is porous, 
hence weathers easily. Jt contains abundant evidence of vertebrate 
fossil remains. Fossils not yet fully identified, but what seem to 
be remains of Plesiosaurus and tracks of other saurians, have been 
found. Squaladont selachin shark teeth abound, as many as a dozen 
having been found under a single square foot of surface. The in- 
vertebrate forms are numerous. Jnoceranus umbonatus, Inoceramus 
undabundus, and other forms, as yet undetermined, have been found. 
The Flagstone Horizon—The Flagstone horizon rests conform- 
ably upon the Lincoln Marble. It consists of three or four layers 
of limestone with intervening shale. The maximum thickness of the 
group is 10 feet. The maximum thickness of the individual layers is 
S inches. The fossil forms in this horizon are not numerous. Re- 
mains of fish, shark teeth and invertebrates, of the genus Jnocera- 
mus, have been found. The limestone is white in color and fine in 
texture. It is used throughout the Benton area for flagstone, hence 
the name. 
The Inoceramus Horizon.—The Inoceramus horizon is nearly mid- 
way of the limestone group, and rests conformably upon the Flag- 
stone horizon. The average thickness is from 4 to 5 feet, and con- 
sists of from one to three layers of limestone separated by argilla- 
ceous shale. The average thickness of the individual layers is 6 
inches. The limestone is composed almost wholly of Inoceramus 
