Fils GAINED CAN VON OF WWE, COLORADO; B27. 
Midway of the lower portion of the shales and limestones of 
the Chuar terrane the presence of a fauna is shown by a minute 
discinoid or patelloid shell, a small Lingula-like shell (which may 
be a species of Hyolithes), and a fragment of what appears to be 
the pleural lobe of a segment of a trilobite belonging to a genus 
allied to the genus Olenellus, Olenoides or Paradoxides. There 
is also a Stromatopora-like form that is probably organic. 
The paucity of the fauna in both the Unkar and Chuarx ter- 
ranes demands some explanation, for the strata were apparently 
deposited under conditions most favorable to the development of 
abundant life. I find in my field-notes a suggestion that the sedi- 
ments were deposited in a great inclosed basin, or mediterranean 
sea, and that during the greater part cf the period of their deposi- 
tion no connection existed by which any fauna then existing 
outside of this sea could obtain ingress. 
The sediments of the Unkar and Chuar terranes, as measured, 
give a total thickness of 11,950 feet. How much more was planed 
away by the sea in which the next terrane (the Tonto) was 
deposited was not determined. With the close of the epoch of 
the Chuar terrane a period of orographic movement ensued, dur- 
ing which the strata of the Vishnu, Unkar, and Chuar terranes 
were elevated, broken by faults, and more or less flexed. The 
summit of the series is now found in a knoll on the divide between 
Nunkoweap and Kwagunt Valleys. It may have been a remnant 
left by the sea as the latter cut away the Algonkian land, or a hill 
remaining above the baselevel of erosion that planed away a 
section of the entire thickness of the pre-Tonto strata. The sur- 
face upon which the sandstones of the lower Tonto were depos- 
ited was nearly level. Here and there a hard stratum caused 
ridges to be left in the Tonto sea, and the fragments broken from 
them are scattered among, and mixed with, the sands of the 
Tonto. 
Of the duration of the interval of erosion between the deposi- 
tion of the sediments of the Chuar terrane and the first of those 
of the Tonto, we can only form a conjectural estimate, based on 
the sections of Cambrian rocks in northwestern and central 
