24 The American Geologist. Jau. isao 
palaeozoic, or older rock regions, can be seen for many miles. 
These are two sub-oval areas extending north and south in the 
geographic center of the state from near Red river to the Col- 
orado, between the 98th and the 99th meridians, and separated 
by the narrow strip of the Grand Prairie beneath which they 
are no doubt continuous. Lithologically this northern region 
is composed of the older and more consolidated sandstones, 
limestones and clays of the Coal Measures with the same 
aspect of soil and flora, much stunted by drouth, and general 
sterility of cultural aspects like the Coal Measures of the 
Appalachian and Ouachita regions. The southern area, in 
addition to these Carboniferous rocks, possesses still older and 
harder rocks, consisting of limestones, sandstones and schists 
of the Silurian (San Saba formation), the Potsdam (Packsad- 
die formation) and the Cambrian (Llano formation) respect- 
ively, accompanied by some remarkable granitic upthrusts 
and domes, some of which, as I have previousl}'^ shoAvn in this 
journal,'" as late as post Carboniferous. For the northermost 
of these areas I propose the name of the Palo Pinto country or 
Coal Region, and for the southernmost, the Llano country, or 
Granite region. 
The detailed stratigraphy and structure of these important 
regions are unrecorded in geologic literature. But it is evi- 
dent from the few cursory examinations I have been able to 
give it that it is what was once a region of much disturbance, 
but not so excessive as the folding of the Ouachitas or Appala- 
chians. While the latter have remained above oceanic inun- 
dation since Carboniforous time, their Texas counterparts Avere 
buried probably beneath thousands of feet of sediments during 
the lower and upper Cretaceous subsidences. It is also quite 
evident that this Older Rock region was the vicinity of the 
continental divide which from late Cretaceous to early Quat- 
ernary time separated the waters of the Atlantic from the 
interior lakes. That they are at present exposed through the 
erosion of the thousands of feet of Cretaceous strata that once 
covered them is evident. Their former extent and their rela- 
tionship to the Ouachita system on the one hand, and the 
Rocky mountains on the other, are still concealed by the over- 
lying Cretaceous rocks. 
^" See a portion of the geologic story of the Colorado, American 
Geologist, May, 1889. 
