PALEONTOLOGIC RELATIONS. 319 



nessee, though I have rarely seen it from a higher liorizon. Several of 

 the species belong properh^ to the Lower Productive Coal Measures. 



PALEOyrOLOGIC RELATION OF NEW RIVER SECTION TO SHARON COAL 



IN OHIO. 



This flora is not presented as proof that it represents the horizon of 

 or is synchronous witli the Sharon coal in Ohio. It illustrates a fact 

 observed in every section of the Pottsville yet examined, namely, that 

 in the thick sections of this series the plants of the Sharon coal are found 

 only in the upper part of the section, and that, though straggling forms 

 begin to appear near the middle of the series, Ave do not find the asso- 

 ciation of species characteristic of the Sharon coal to prevail and stand 

 forth predominantly until we near the top of the series. In every case 

 the paleontology of these greatly thickened sections of the Pottsville 

 shows the stage of the Sharon coal to be in the upper half of the series 

 and relatively high therein. Although its fossils relate it closely to the 

 Sewanee of Tennessee and the coal-bearing shale of Washington county, 

 Arkansas, even allowing for a higher range of the species in passing 

 southward, it can hardly be older than the main Sewanee, while there 

 is some evidence that it is more recent. I can find no satisfactory pale- 

 ontologic support for the view * that " this Sharon bed and its thin rider 

 appear to represent all the coals in the New River group." 



Equivalence of Pottsville Sections. 



The foregoing paleontologic evidence has a direct bearing on the im- 

 portant question of the equivalency of the various sections of the Potts- 

 ville in the different portions of the Appalachian basin. The ojnnion 

 seems generally to prevail that the time covered by the Pottsville series 

 in the various portions of the Appalachian trough is the same, or very 

 nearly the same, and that the verv thick sections simply represent ex- 

 pansions of some or all of the meml)ers present in the tliin sections. 

 Thus Professor I. C. White, in his invalual)le ])ulletin on the stratig- 

 raphy of the bituminous coal field,t argues that the Virginia-Kentucky 

 section, 2,000 feet or more in thickness, represents an expansion of a 

 series never over 300 and sometimes less than 200 feet thick in Ohio. If 

 this be true, then the lower l,50fJ feet, in round numbers, of the south- 

 ern section must cover the time represented by the " Sharon conglom- 

 erate," a formation only from 20 to 40 feet thick, or even wanting in 

 places, in Pennsylvania and Ohio. On the contrary, the evidence of the 



•See I. C. White : Bull. U. 8. Geol. Survey, no. 66, p. 202. 

 tOp. cit., pi. ii, fig. 2. 



