298 CENTRAL MINERAL REGION OF TEXAS. 



posed on Glen Creek,* also along the James River southward, where 

 their thickness is probably as great as anywhere in Central Texas, f Other 

 outcrops occur in the San Saba River valley in the northern part of Mason 

 County. The same beds appear in goodly quantity in the Silurian escarpment 

 which runs irregularly east and west along the upper bluffs north of Fairland 

 Postoffice in Burnet County. This division sometimes directly covers the 

 Potsdam limestone division of the Katemcy series, but it has not as great a 

 distribution over that terrane as have some of the earlier and probably some 

 of the later beds. There is considerable variation in thickness in different 

 sections, but the maximum, so far as observed, can not be much above 60 to 80 

 feet. The rocks are chiefly brown weathering dolomites or semi-crystalline 

 limestones of dark reddish or purplish color, becoming sandy or granular 

 above. For a general description, perhaps the expression brown, shaly, mag- 

 nesian limestones will be most applicable. The beds are rather thinly lami- 

 nated, and they usually weather into craggy cliffs wherever there is any 

 opportunity for such a topographic feature. This is well shown along a part 

 of Hudson Creek, north of Camp San Saba, McCulloch County, and in the 

 valley of James River and some of its tributaries in Mason County southwest. 

 This last area is continued northward across the valley of Mill Creek; thence 

 beyond the Llano River to the lower valley of Leon Creek. Good exposures 

 also occur over much of the eastern edge of our district, but in places the 

 higher beds seem to have overlapped so far as to cut out the members of 

 the Leon series. 



Making the base of the Hoover Division at the horizon assumed provision- 

 ally in this report, no fossils have been found in any rocks which are cer- 

 tainly referable to the "Wyo Division. In a number of widely separated out- 

 crops search has been made without success, but much more detailed work 

 is necessary before abandoning the quest. Badly broken Trilobite remains 

 occur in beds on Leon Creek which may belong at the base of this Division, 

 but the lithologic characters caused me to consider them Cambrian in the field. 



C. HOOVER DIVISION (CHAZT?). 



Overlying the Wyo Division of the Leon Series in many exposures, but 



*This creek enters the James River from the west about two miles below the mouth of 

 Devil's River, near the north line of original survey No. 334, Mason County. As it has not 

 previously been named, it will appear upon our maps as G-len Creek. This name is sug- 

 gested by the gorges and coves along the crooked stream course, but it is also true that a 

 Mr. Grlen has recently occupied the ranch house in Schreiner's pasture, directly in the path 

 of the creek. 



f The writer has reserved the study of the upper valley of James River for the field season 

 of 1890. Enough was seen in 1889 to make it very probable that results of very great in- 

 terest will accrue from instrumentally accurate sections made in that region. 



