LIMESTONES OF WESTERN TENNESSEE 685 



den road, and at other points along the Big Sandy River. The 

 Linden bed is exposed along the Cumberland River, a mile west 

 of Cumberland City, and on the eastern side of the railroad, a 

 quarter of a mile south of the home of John Broadus. Owing to 

 faulting, it is impossible to determine the thickness of the Linden 

 bed in the Wells Creek basin, but, as far as may be judged from 

 the exposures seen, it does not exceed 30 feet. East of the home 

 of John Broadus the exposure of the Linden bed does not exceed 

 10 or 15 feet. Mr. Charles Schuchert found three specimens of 

 Camarocrimis in Benton county at an undetermined horizon. 



As far as may be judged from the few sections so far studied, 

 Camarocrimis is abundant in the lower half of the Linden bed, and 

 is either much rarer or altogether absent in the upper half. The 

 upper half, on the contrary, appears to contain a greater quantity 

 of softer, clayey material, which weathers readily. It appears to 

 give rise to the greater number of exposures at which the Linden 

 bed fossils may be collected free from the rock. It appears pos- 

 sible to divide the Linden bed into two subdivisions, a lower, 

 Camarocrinus or Ross limestofie, and an upper, or Pyburn limestone. 

 The exposures at Perryville, Linden, and Cumberland City appear 

 to belongto the upper or Pyburn horizon. The upper bed appears 

 to have a greater eastward extension than the lower, overlapping 

 the latter. Very little attention has been given so far to the 

 stratigraphy of the Devonian in western Tennessee. The chief 

 results of the writer's efforts have been the conclusion that the 

 Linden bed is absent in a large part of the territory east of the 

 Tennessee River once believed to contain it. It is not known to 

 occur anywhere between Rise mill, New Era, Bath Springs, 

 Economy, and Martin's mill. 



12. The Camden chert. — As in the case of the Linden bed, the 

 thickest sections of the Camden chert are found at the more 

 western points of outcrop. At Linden, on the eastern edge of 

 the town, at the spring near the foot of the hill, it is represented 

 by a massive gritty limestone, only 2 feet thick, immediately 

 beneath the Hardin sandstone. In this rock were found two 

 ventral valves of Spirifer, silicified, showing both the exterior and 

 also the large muscular scars in the interior. They were identi- 



