176 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



Safford, in 1869/ divided the Lower Carboniferous of Tennessee 

 into two groups, designated in ascending order as " (8a) Siliceous 

 Group," and "(86) Mountain limestone." His Mountain limestone 

 included everything between the St. Louis and the Coal Measures, 

 i. e., the Kaskaskia. The Siliceous group he subdivided into two 

 members, the "Upper or Lithostrotion bed," equivalent to the St. 

 Louis limestone of the Missouri geologists, and the "Lower or Pro- 

 tean member," includmg everything from the St. Louis down to the 

 Black slate. He considered this member as "more especially the 

 equivalent of the Keokuk limestone" (p. 342), but adds that "it 

 contains, however, some Burlington forms." His descriptions and 

 sections show it to be of a variable character, but in a general way 

 to be composed of argillaceous beds, or shales, in the lower part, 

 and more or less siliceous, or cherty, limestones in the upper, with 

 irregular occurrence of limestone bands among the shales and cherts. 



The Lower or Protean member of Safford's Lower Carboniferous 

 corresponds to Lyon's bed P; and the name "Knobstone," as men- 

 tioned by Lyon, has been given to it currently because of its exposure 

 in many of the isolated liills, or "knobs," which form a conspicuous 

 feature of the topography of southern Indiana and northern Ken- 

 tucky. But it extends over a wide area in Kentucky and Tennessee 

 where the knobs do not occur. In the latter state it has received 

 the name of "TuUahoma formation," and is appHed to such well- 

 known localities as Whites Creek Springs, Tenn., and Allen and 

 Metcalfe counties, Ky., at all of wliich species of undoubted Keokuk 

 type occur. In Indiana the name "Knobstone" is adhered to, as 

 given by Owen in 1859.^ In the earlier reports of the State Geological 

 Survey a clear distinction was recognized between the Knobstone 

 shales, with intercalated calcareous layers, the succeeding Burling- 

 ton, and the Keokuk limestone beds. In the report for 1878 (p. 379) 

 some good sections are given of exposures in Harrison County, 

 wliich is a westward continuation of the Kentucky knob region, 

 showing over 200 feet of Knobstone shales and sandstones, including 

 at the upper part 8 to 15 feet of thin bands of "red encrinital lime- 

 stone," and above that, after several different beds of various colored 

 siliceous clays, slates, flints, and cherts of from 30 to 70 feet, heavy 

 Keokuk crinoidal limestone to a thiclcness of 40 feet or more. An 

 earlier report, 1874 (p. 115-118), recognized the Knobstone as dis- 

 tinct from the Burlington and Keokuk, and treated the part con- 

 sisting of sandstones and underlying bluish and greenish (New 

 Providence) shales as equivalent to the Chemung, Waverh'^, and Kin- 

 derhook. It says that the "Button-mould wash," so called from the 

 disk-shaped segments of crinoid stems found in it, is but another 



1 Geology of Tennessee, p. 339. 



2 Keport of a Geological Reconnoissance of Indiana Rocks in 1S39, t). 21. 



