074 P. E. RAYMOND TRENTON OF TENNESSEE AND KENTUCKY 



Glens Falls of New York. The Jessamine is comparable to the familiar 

 IVasopora beds of New York and Ontario. Numerous differences be- 

 tween the two could be pointed out, such as the abundance in Kentucky 

 of Rhynchotrema increbescens and Hebertella franhfortensis, the rarity 

 of trilobites, and absence of such guide fossils as Triplecia, Trematis, and 

 Parastrophia ; but there are, perhaps, as many similarities as could be' ex- 

 pected, taking into consideration the geographical situation. 



With the Benson, Platystrophia reenters, and it may or may not be 

 significant that representatives of this genus are very rare in the lower 

 175 feet of the Trenton at Trenton Falls, New York. 



The Woodburn is marked by the appearance of Columnaria for the first 

 time above the Curdsville, but otherwise its fauna shows nothing remark- 

 able. The whole series to this point, with a thickness of about 200 feet, 

 is fairly closely comparable to, and to be correlated with, the lower 226 

 feet of the composite section of the Trenton at Trenton Falls and on 

 Eathbone Brook, New York. 5 This is practically the conclusion which I 

 reached in 1916, but which opinion has been strengthened on seeing the 

 exposures in the field. 



Before discussing the correlation of the Perryville and higher strata, 

 it is well to review the situation in Tennessee. 



The Section in central Tennessee 



The basis of modern knowledge of the Trenton of the Nashville dome 

 is the work of Ulrich, published in best form by Hayes and Ulrich in the 

 Columbia folio of the U. S. Geological Atlas, 1903. 



In this region the highest Ordovician formation is generally either the 

 Fernvale (Eichmond) or Leipers (Maysville) and the present practice is 

 to consider the Catheys as the highest formation of the Trenton. The 

 following section, given in descending order, will, however, include the 

 Leipers : 



Leipers. — Granular blue limestone, sometimes earthy, knotty, and shaly ; very 

 fossiliferous. Thickness, 0-100 or more feet. 



Catheys. — Thinly bedded, fine grained earthy and shaly limestone with nu- 

 merous fossils. Thickness, from 50 to 120 feet. 



Bigby. — In the typical region, which is in the vicinity of Columbia, this is a 

 granular, crystalline, phosphatic limestone, without shale except locally 

 at top or bottom. Thickness, 50 to 150 feet. 



Hermitage. — Thinly and thickly bedded limestone with some shale. Thick- 

 ness, 40 to 70 feet. 



5 Raymond : Bull. Mus. Comp. Zool., vol. 56, no. 3, 1916, p. 253. 



