210 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



between the Black slate and Pentremital limestone, was called the 

 Siliceous group. This group was subdivided in ascending order into 

 the Siliceous beds and the Cherty limestone. The lower member, 

 the true Siliceous beds, about 200 feet thick in the northern part of 

 the state, consists of a fine-grained, siliceous, light blue, rather 

 unfossiliferous limestone, which, upon weathering, leaves a light 

 yellow to brown soil strewn with chert fragments. The cherty lime- 

 stone proper differed "in being a true limestone affording a brick- 

 red soil, in the character of its interbedded [flint] masses and in being 

 much more fossiliferous." A species of Lithostrotion (Lonsdalia 

 canadensis) was registered as one of the fossils. 



In 1856 ^ Safford described the same strata under the same name, 

 giving little additional information regarding the rocks. 



In his well-known classic work, "Geology of Tennessee," 1869, 

 Safford gives an excellent description of the Siliceous group, dividing 

 it into the "Lower, or Protean bed," and the "Lithostrotion Coral 

 bed." The Lithostrotion bed is characterized everywhere by L. 

 canadense, and Safford correlates it with the St. Louis limestone. 

 The lower or Protean member is said to be "in general equivalent to 

 the divisions of the Lower Carboniferous limestone lying below the 

 St. Louis limestone. It is, perhaps, more especially the equivalent of 

 the Keokuk limestone; it contains, however, some Burlington forms." 

 As Mr. Springer has indicated, the fact that most of the Lower Sili- 

 ceous fossils listed by Safford are Keokuk species outside of Tennessee, 

 b?as led to the correlation of these beds almost invariably with the 

 Keokuk. This opinion is indicated in the "Table of Geological 

 Equivalents" (by A. Winchell), on page 364 of the "Geology of Ten- 

 nessee," where the Lower Siliceous is correlated with the Keokuk 

 limestone of Iowa and Missouri, and with the Keokuk and Knob- 

 stone of Kentucky, while the Burlington and underlying Subcarbon- 

 iferous strata are indicated as wanting in Tennessee. 



Safford and KilHbrew use the term Barren group instead of Protean 

 bed for these strata in 1874 in their "Resources of Tennessee." Later, 

 in their textbook "The Elements of the Geology of Tennessee," pub- 

 lished in 1900, they abandon both the names Siliceous group and 

 Barren group, substituting for these, respectively, St. Louis Hme- 

 stone and Tullahoma limestone, and introducing the new term Maury 

 green shale for the basal member of the series in Maury County. 



The next work upon the subject, so far as it relates to Tennessee, 

 is bj» Hayes and Ulrich,^ who adopt the names Tullahoma formation 

 and St. Louis limestone, but include and map the Maury green shale 

 with the Chattanooga black shale. In the Tullahoma formation they 

 describe a lower calcareous shale member and state that it is fre- 



1 Geological Resources in the State of Tennessee, First Report, p. 159. 



2 Columbia Folio, Tennessee. U. S. Geol. Surv., Folio No. 95, 1903. 



