432 ©. D. Walcott—Paleozoic Rocks of Central Texas. 
erosion of the Llano group ae before the deposition of the 
otsdam. It is to this age that the great masses of granite 
belong. At the crossing of the Llano river, on the road from 
Burnet to Honey Creek Cove, fragments of the shales and 
sandstones of the Llano group may be seen imbedded in the 
granite, and on Morgan’s creek, Burnet Co., the Potsdam rests 
directly on the granite. 
he thickness of the Llano group was not determined owing 
to lack of time to study it in detail. In Honey Creek reel 
from two to three thousand feet of shales, sandstone and lim 
stones were observed, and parennses - the town of Llano : 
great mass of reddish sandstone oc 
On Roessler’s map of Llano ok ; all of the ula i is 
referred to as “ granitic, metamorphic and igneous,” and 
been considered as Archean. The a did not pe Ba on 
rocks of undoubted Archean age. No fossils were found in 
the Llano group, but, from its lithologic character and position 
in relation to the overlying Potsdam, I refer the group to the 
Paleozoic, and correlate it with the Grand Cafion groups which 
are of Paleozoic age and referred to the Lower Cambrian. 
Pati OF Sacto ase SHOWING THE Uscomronsirs BETWEEN THE 
PoTsDAM AND LLANO GRO 
1 = Llano group. 
mn ener Potsdam —, 205° feet. 
m limeston 310° 
. Ponies nig 30° 
5 = Potsdam sandstone . 60 
605° 
POTSDAM. 
The Potsdam horizon has been well described by Shumard.§ 
The writer collected several thousand specimens of fossils from 
* It may be that further and more complete abate bag yy will prove all paid 
granite to have been intrusive in the Llano Group r to its erosion, but fro’ 
the ev aor as seen by the writer, it is difficult to eae ha its occurrence eX xcept 
as abov 
an of Llano county, Texas, A. R. Roessler, New York, 1 
¢ Since the paper on t the Pre-Carboniferous strata of the ont Cafion was pub- 
lished (this Journal, vol. xxvi, p. 487), a fragment a. a trilobite, probably of the 
genus oparia, a. has been detected in a bit of shale from the Chuar group. 
§ This Journal, IJ, vol. xxxii, p. 213, 
