794 FLORAL ZONES OF THE POTTSVILLE FORMATION. 



the tield, as iwoak'cl hv l)oi'iii*4S not far from the LiiK-oln region.' eun 

 not fail as convincing arguments against the free application, in the 

 Pottsvilh' formation of the Southern Anthracite field, of the correl- 

 ative methods employed by geologists working in the interior of the 

 Appalachian trough, where, in the several l)ituminous ])asins. the beds 

 are relatively uniform and clearly persistent over great art^as. That 

 one of the thin coals occurring in the Pottsville Gap section nearly 

 700 feet below the Twin coal is contemporaneous with and equivalent 

 in point of time to a portion of the Xo. -i coal at Lincoln or Williams- 

 town is perhaps not improbable, since the favorable conditions for 

 exclusivelv carbonaceous deposition luay have 1)een synchronous at 

 both points, and the testimony of the fossils points toward the latter. 

 It is lilvcwise possible that the 1-foot coal accompanying tlie 2 feet of 

 dark shales at bed C may represent Lykens coal No. .'). It is. how- 

 ever, extremely improl)able that either of these coals extends in a con- 

 tinuous carbonaceous terrane from the type section at Pottsville to 

 the very valuable deposit in the Lincoln district. 



The stratigraphic position of l)ed A in the topmost stratum of red shale 

 at the ])ase of the section probably justifies the assumption that it is 

 older than any of the Lykens coals. Its very small flora, of Lower 

 Carbon if (>rous facies, appears to warrant this assumption, altliough it 

 is too mcniger to serve as a foundation for satisfactory comparison. 



FLORA OF THE LOWER INTERMEDIATE DIVISION. 

 milKF EXISTENCE OF A TRANSITION EEOKA. 



The relative distinctness, from a stratigraphic stanflpoint. of the 

 floras of the Upper Lykens division, as compared with those of the 

 Lower Lykens division, has already lieen remarked in connection with 

 the proposed subdivision of the Potts\ille formation according to the 

 concomitant grouping of the economic coals and the fossils. It may 

 be noted at this point that the paleontologic difl'erenct^ l>etween the 

 lower and the upper groups, which, excluding th(»gynmosperms and 

 certain vertically widely distributed Lj'copodiales. have comparativeh' 

 few species in common, is probably due in part at least to the interval 

 1 (('tween Lykens coals Nos. 4 and 3. which is about 250 feet in the Lin- 

 coln region. This interval, of wiiicli we have from the Lincoln region 

 no paleontologic re})r('sentation in the collections, and which is there- 

 fore not assigned to either the upper or the lower division, still rcMuains 

 accordingly a paleontologically unknown (piantity. Yet. notwithstand- 

 ing the inferential conclusion that it contains a transitional mingling of 

 U})per and Lower Lykens floral characters, such as occurs in the inter- 

 \Til (Lower Intermediate division) l)etween .570 and 700 feet below 

 the Twin coal in the type section, the vertical distance involved is 



1 See the records of diamond-drill lx)re holes on Broad Mountain, platted in groat detail on colnninar- 

 section sheet ix, Atlas Southern Anthraeile Field, I't. IV. 



