248 W. N. LOGAN 
As these occupy much the same stratigraphical position they are 
very likely of the same age. The Lzoplacodes seems to be identi- 
cal with that described by Meek in the Geology of the (Ulpipies 
Missouri. 
23. Drab-colored clay, 70’. Species of the genera Svonto- 
saurus, Diplodocus, Morosaurus, Stegosaurus and Allosaurus occur 
in this horizon. Portions of species of all these genera were 
found in one quarry by the Kansas University collecting party of 
which the writer was a member. The clay is of that quality 
usually designated as joint clay. It contains, in places, iron and 
argillaceous concretions of small size. The iron and sometimes 
the bones are covered with small selenite crystals. 
24. Grayish-white sandstone, 50’. This layer forms a con- 
spicuous capping for the hills, and is the highest remnant of the 
anticline. It breaks up into large blocks, which lie scattered 
along the slopes of the underlying softer beds. Its erosion and 
disintegration is accomplished chiefly by sapping. No fossils 
were found in this stratum” (Dakota ?). 
The maximum thickness of the Jura for this bese does 
not at the most exceed 100 feet. All of the fossils are found in 
a vertical range of but little more than half that distance, and 
yet the fauna includes all the characteristic species of the 
interior Jurassic province. The beds are heterogeneous and 
indicate constantly varying conditions of sedimentation. 
The entire section is given in its minutest details so that an 
idea of the general character of the Como beds may be obtained. 
In many localities this formation has been included in the Jura, 
although the Jura is wholly marine while on the other hand the 
Como is wholly fresh water. On the whole the marine beds are 
more calcareous but there is usually at least one thin bed of 
limestone in the Como. The lithological characters of the beds , 
do not always stand out so clearly that the evidence of fossils 
is not required to separate the beds. 
Como Lake.—Vhe stratigraphical conditions of the formation 
at Lake Como are not essentially different from those of the 
1 LOGAN: loc. cit. 
