394 GEOLOGY OF NORTHWESTERN TEXAS. 



R. mutata, Hall. Synocladia biserialis, Swallow. 



Spirifer earner alus, Morton. Schizodus wheeleri, Swallow. 



S. planoconvexus, Shumard. Syringaporamultattenuata, McChesney. 



S. Uneatus, Martin. Terebratula bovidens, Morton. 



S. rockymontanus, Marcou. Tainoceras cavatum, Hyatt. 



Spiriferena Jcentuckensis, Shumard. Zaphrentis gibsoni, White. 



Syntrielasma hemiplicata, Hall. Z. spinulifera, White. 



PERMIAN. 



It is intended to include in the Permian all the Red Beds in Texas which 

 lie between the upper part of the Albany Beds of the Coal Measures and the 

 Dockum Beds, or the lower part of the Triassic as recognized here. 



The rocks of the Permian series comprise limestones, sandstones, shales, 

 red and blue clays, and beds of gypsum. There has heretofore been a great 

 deal of confusion in regard to the "Red Beds" of Texas and other localities 

 in the northwest, and they have been sometimes referred to one series and 

 sometimes to another, depending upon the locality at which they were ob- 

 served. 



The strata seen by Marcou in 1853 did not embrace much of the Permian of 

 Texas, as his route was entirely north of the northern extension of the great 

 body of these beds. He saw the upper part of the formation and recognized it 

 as Permian. What he calls Trias in some of his later publications is what I 

 have described as the Dockum Beds (Trias), and is not included in the Permian. 

 What others have seen in Kansas and New Mexico and called Triassic is no 

 doubt correctly designated ; but these beds are not the same as the Permian of 

 Texas, which is here so clearly marked by well defined horizons that there is 

 no occasion to be mistaken in relation to its extent when seen upon the ground. 

 The Permian Beds are so referred on stratigraphic and paleontologic grounds, 

 as will be seen elsewhere in this Report. 



BOUNDARY. 



The entire boundary of the Permian has not yet been definitely determined 

 in Texas. I have traced (and stated elsewhere in this Report) the line of 

 contact between it and the Coal Measures on the east. On the south it is 

 overlaid by the Cretaceous, and there the formation is found to be not more 

 than thirty miles wide. The southern and western line between the Creta- 

 ceous and the Permian, beginning at a point on Kickapoo Creek, in Concho 

 County, near where the road from Brady to San Angelo crosses that creek, 

 passing along a few miles south of San Angelo to the mouth of Spring 

 Creek; thence northward along the Cretaceous hills three or four miles west 



