58 
Transactions Texas Academy of Science. 
Cummins^ W. F. 
Jules Marcou, ^v;llo was at that itime geologist with the Pacific E^ailroad 
iSurvey, from Fort Smith to the Pacific Coast.” 
-X- * -X- * * -X- * 
“The estimated thickness of the strata of the Permian is atout 2800 
feet. A detailed section has been made across the formation, but a general 
section has not yet been made up so as to determine the exact thickness 
of the strata. 
“The dip of the strata is about 40 feet per mile, north 45 degrees west. 
At one locality the dip was calculated by an actual instrumental measure- 
ment of ten miles, at another place of five miles, and at a great number 
of places of smaller distances, so that the dip of the strata is well deter- 
mined. 'It is only at the western edge of the Double Mountain beds that 
there is any increase in the dip, and in that locality the strata are so much 
distorted and folded that it was difficult to get long lines of observation, 
so that the general dip could be determined with anything like certainty. 
There were no faults found nor any evidence of eruptive disturbances. 
“For convenience the strata are here divided intp three beds, whese 
correlation with the Permian formation in other localities will not be 
attempted in this report. 
“Beginning with the lowest or eastern, we have: 
1. IThe Wichita Beds. 
2. The Clear Fork Beds. 
3. The Double Mountain Beds. 
“These beds, from the nature of their constituents and of their forma- 
tion, so grade into one another that the exact line of demarkation is very 
obscure, even if it can be found at all. This is no less the case with the 
line between the Permian and the underlying Coal Measures. A separation 
of these series from the Coal Measures is, however, based, first, on litholo- 
gical differences; second, on fossil contents. 
“The strata of the Coal Measures are not persistent in character on the 
line of contact between that formation and the overlying Permian; and 
yet in each locality there seems to have been a continuous sedimentation. 
On the line of contact between the Coal Measures and the Wichita Beds, 
from Bed iRiver iSiOuth to the Brazos, there are only sandstones in both 
strata; yet there was a oonsiderable lapse of time between their depo- 
sition, as is shown by the fact that the limestones, which at other places 
constitute the highest beds of the Coal Measures, and which at those places 
overlie the sandstones, are entirely wanting along the line of this contact. 
\Further south, on the line of oontaet between the Coal Measures and 
the Clear Fork Beds there are only limestones, which are apparently con- 
tinuous in sedimentation, yet we know that such is not the ease, for only 
a few miles north of this line of observation we find that the Wichita Beds 
of the Permian underlie these Permian limestones. 
“iThe fact of the want of continuity of sedimentation between the Coal 
Measures and the Clear Fork Beds is shown also by the fauna of the two 
beds. The fauna of tbe iCoal Measures limestones, which lie directly below 
the limestones of the Clear Fork Beds, is abundant and consists of such 
characteristic forms as Productus semi-reticularis, Ghcetetes gracilis, Schi- 
zodus wheeleri, Allorisma sub-cuneata, Hemipronites crassus, etc., but 
they almost fade out before they reach the top of the series, and only a few 
