802 FLORAL ZONES OF THE POTTSVILLE FORMATION. 



sented ])y the more rigid, eotir.se-nerved, irregularly dissected, broad- 

 toothed form more characteristic of the Lower Coal Measures ; not 

 by the very narrow, lax-leafed type, Avith thin nerves, described by 

 Lesqiiereiix^ as Sjj/icuoj>/ii/I/w/i sa:i'(fi'a(j(i:'f(>liiuii^ from beds of Upper 

 Lykens age in Washington County, Arkansas. The Sigillaria Icevi- 

 gata is at once suggestive of the Coal ]\Ieasures. The g^-mnosperms, 

 on the other hand. l)elong to species Avhich have generalh' a relativel}^ 

 wide range in the higher part of the Upper LA^kens division in other 

 coal fields, and which are hardh' known from the Lower Coal Measures 

 of the Northern States. These comprise species that are especially 

 common in the upper portion of the formation, of which Caniiocarpon 

 annuldtain. A\u\ C. hicusj)idatum Yiiv. oliioense appear to bo distinctly 

 characteristic, the former being more restricted to the upper beds. 



From the foregoing it appears that in beds M and N we have a flora 

 the pteridophytic elements of which are, on the whole, generally dis- 

 tinct from those characteristic of the preceding zones of the Pottsvillo 

 formation. The gA'mnosperms, on the other hand, are character- 

 istic of the Upper Lj^kens division. Yet the ferns, though identical 

 or closely related to those of the Lower Coal ]Measures, appear not to 

 exhibit the forms and facies of the species found either in the roof of 

 the Buck Mountain coal (Lower Coal Measures) or in the Brookville 

 or Clarion coals of the Allegheny series, in the bituminous basins of 

 the Northern States. The wide difference between the floras of the 

 preceding- zones of the Upper Lykens division of the Pottsville for- 

 mation, on the one hand, and those of the Lower Coal Measures, on 

 the other hand, has already been indicated, and will be further shown 

 on a later page. Between these two sections — between the flora of 

 Lj'kens coal No. 1. or of bed L of the type section, and the roof of the , 

 Buck ^Mountain coal, or base of the Lower Coal Measures in the 

 anthracite fields — we have an interval of about 375 feet, within which 

 occurs a very distinct, though perhaps gradual, change from the purely 

 Pottsville plant life to the flora which, as we shall presentl}" see, is 

 distinctly that of the Lower Productive Coal Measures, as that group 

 is recognized in the coal fields of the Northern States. The small 

 collections obtained from the partings, beds M and N, in the upi)er 

 plexus of massive conglomerates, which occurs within the top of the 

 Pottsville formation as generally defined on a lithologic basis, appar- 

 ently constitute fragments in evidence of this floral transition. For 

 the present, when speaking of the type section and region, and until 

 the subject is treated in a broader light, in connection with the Potts- 

 ville of the other portions of the Appalachian province, I shall continue 

 to use the term '""Upper Litermediate division" in referring to this 

 portion of the Pottsville formation. 



1 Coal Flora, Vol. Ill, p. 720, pi. xciii, fig 9, 9a. 



