W ILEISTON. | The Kansas Niobrara Cretaceous. 239 
veins the calcite crystals are often very pure and perfect, intermixed 
more or less with crystals of barite. I have never observed foreign 
material in them. I doubt not that they represent simply cracks 
from drying, the crystals formed from infiltration. Possibly, how- 
ever, the numerous local disturbances in the formation may indicate 
other causes. Plates XXXII and XXXIV. 
The material of which the Ornithostoma beds is composed is true 
chalk throughout their entire thickness. There is no marl, no sand- 
stone or other material. The color varies, often within short dis- 
tances from a light blue to a lavender, a white, a buff, a yellow or 
even a red. This color is, however, not confined to any horizon, 
save that the lower horizons have the color usually lighter blue or 
purer white. The yellow color with its varying shades of red where . 
much exposed is confined to the upper beds, and the line of separa- 
tion is very easily traced from the Smoky Hill east of Monument 
Rocks to the Saline north of Wa Keeney, and thence to the South 
Fork of the Solomon near Lenora. Not only is the color line easily 
traced, but the fossils contained in them are characteristic. For 
convenience I will call them the Hesperornis beds and the lower 
strata the Rudistes Beds. The impurities of the chalk vary from 
less than two to about ten per cent. 
It is strange that the division into chalk and shale beds should 
have been persistently adhered to by writers on the Kansas Creta- 
ceous since the time of Mudge. As I have already said more than 
once there is no such geological distinction. As a usual thing the 
jue chalk and its weathered blue shales are found lower down in 
the valleys of the rivers or their tributaries, that is, where it is more 
or less saturated with water. Almost always borings for wells 
encounter the blue chalk, not white or yellow. Furthermore fre- 
quently one will observe the blue chalk changing to white and yellow 
as it passes outwards from the water courses, and this change may 
take place within a few yards distance. Pure white or yellow homo- 
geneous chalk may be traced through every foot of the entire thick- 
ness from the Fort Hays to the Fort Pierre. I trust the myth of chalk 
and shale beds will not be again repeated. Wherever the chalk is of 
a deep blue color, when exposed it becomes shaly, loose and friable, 
broken up apparently by the action of the pyrites which such beds. 
