LIMESTONES OF WESTERN TENNESSEE 695 



Fauna," in which the Oriskany age of the upper part of the beds 

 hitherto included in the Linden bed was shown. Therefore, in 

 1900, in a second edition of the Geology of Tennessee^ Safford and 

 Killebrew restricted the use of the name "Linden limestone" so 

 as to include only beds belonging to the Helderbergian as now 

 defined, while the name "Camden chert" was given to the Oris-- 

 kanian strata formerly included in the upper part of the Linden 

 limestone. The Linden limestone as now defined appears most 

 nearly equivalent to the Delthyris or New Scotland bed. 



The Camden chert was placed by Schuchert in the lower part 

 of the Oriskanian. He called attention particularly to the 

 absence of the characteristic upper Oriskanian species : Hip- 

 pariofiyx proximus, Choiwstrophia complanata, Spirifer arenosus, 

 Re?isselaeria ovoides, Meristella lata, Camarotoechia pleiopleura, C. 

 barrandei, and C. speciosiis. Since his paper appeared a specimen 

 related to C. pleiopleura was found loose in the sand above the 

 Linden bed at Perryville, and a Spirifer resembling Spirifer imicus 

 was found in the top of the Camden bed at the Whirl in the 

 Buffalo River north of Bakerville. 



The use of the name "Linden limestone" for the Helderber- 

 gian section in Tennessee is unfortunate, since at the type locality, 

 Linden, the Helderbergian does not exceed 17 feet in thickness, 

 while the maximum thickness in the state exceeds 100 feet. 

 Moreover, the Helderbergian at Linden is overlaid by a thin 

 section of Camden chert, 2 feet thick, hitherto included in the 

 Linden bed. The Linden bed at Linden apparently belongs to 

 the upper, more clayey part of the Helderbergian section as 

 exposed in Tennessee, overlying the Camarocrinus beds. How- 

 ever, too little attention has been given as yet to the stratigraphy 

 of the Devonian limestones of Tennessee to warrant a definite 

 conclusion. 



F. THE COFFEE SAND. 



At various localities along the Tennessee River, in Hardin 

 county, the paleozoic formations are overlaid by yellowish sands, 

 sometimes interstratified with beds of clay. They have been 

 called the Coffee sand by Professor Safford, and are believed to 

 be equivalent to the Tombigbee sand, referred to the Lower 



