302 THE CAMBRIAN. [uull.81. 



The calcareous bands in the lower part of the division are not numerous; toward * 

 the top, tbey generally become more abundant, increasing as we ascend, until finally 

 the shales disappear, and the blue ooliticlinie stone, and dolomites are the only 

 rocks. In this way the shale division runs into the uppermost one. 



In the northeastern part of the State the shales, as a division, are not well charac- 

 terized. As already stated they are much mixed with beds of limestone and dolo- 

 mites, and lose, in good part, their distinctive features. Moreover, in this region 

 there is little oolite rock. A portion of the shale appears to be replaced by a blue 

 limestone containing thin clayey seams, which give the surface, especially when 

 weathered, a striped appearance. This striped rock occurs, too, further south, its 

 place being at the top of the shale. 



The thickness of the Knox shale is not easily determined. What is said in refer- 

 ence to the thickness of the strata in Poor Valley * * * applies generally. AVe 

 may place it as an approximation at 1,500 or 2,000 feet. 1 



Prof. Safford states that fossils occur in a blue limestone intercalated 

 with shales, sometimes quite abundantly, both in the compact and oolitic 

 layers. Toward the top of the division and in the blue rocks of the 

 succeeding division they are seen at many points. The shales them- 

 selves are occasionally fossiliferous. It was his intention to describe 

 the species in the appendix of the volume, but we find only a list of 

 names, as follows : 2 



Crepicephalus similis, Safford. 



roanensis, Safford. 



tenuesseensis, Safford. 

 Lonchocephalus fecundus, Safford. 

 Agnostus arcanus, Safford. 

 Lingula prima?, Conrad. 



A large collection has been made within the last few years at the 

 localities from which he obtained his specimens, and from many others 

 in Tennessee, that indicate this fauna to be a portion of the Upper 

 Cambrian or Potsdam fauna. The same fauna extends up into the base 

 of the limestone for a short distance. The entire dolomitic series is 

 referred to the Knox group by Prof. Safford, but I think that the line 

 of demarcation must be drawn near the base of the dolomite. 



As a whole, the Cambrian group in Tennessee is represented by a 

 great series of sandstones at the base, succeeded by a series of shales 

 that become more and more calcareous toward the top, where they pass 

 into the dolomitic series, forming the base of the Silurian (Ordovician) 

 system. During the progress of the resurvey of eastern Tennessee by 

 the geologists of the U. S. Geological Survey Dr. Cooper Curtice found 

 a few fossils in the shales interbedded in the quartzite of Chilhowee 

 Mountain, and in 1889 I found a few specimens in the shale about 20 

 feet above the quartzite in the upper shale bed. The study of the fos- 

 sils collected by Dr. Curtice and myself proves that the Olenellus or 

 Lower Cambrian fauna occurs in the shales of the quartzite series of 

 Chilhowee Mountain. This fauna, with that found in the upper portion 

 of the Knox shales and the base of the dolomite, gives two distinct 



1 Op. cit., p. 211. * Op. cit., p. 212. 



