870 FLORAL ZONES OF THE POTTSVILLE FORMATION. 



Nervation distinct, smooth, depressed in tlie lower portions of the 

 pinnules: primary nerve rather coarse, distinctly derived somewhat 

 obliquely from the depressed axis of the rachis, forking at a more or 

 less open angle in the base of each lobe or division, and passing with 

 ver}' slight geniculation, while diminishing, to its vanishment at the 

 apex of the pinnule; nervil of each compound lobe or division forking 

 pinnateh' at a rather open angle, usually in the lower part of the 

 division, to supph' a nerve for each ultimate lobe or tooth. 



The plant described above differs from other species of the genus 

 yet known to me by its relativeh^ short, broad, laterally convex ulti- 

 mate divisions, which are, nevertheless, well separated. The final 

 pinna> are relatively short and compact. This feature as well as the 

 form of the lobes, which in the inferior t)asal pinnules are sometimes 

 palmately spread, as in Eremopteris missourlensis Lx., is one of the 

 more prominent characters b}^ which the plant differs from Eremop- 

 tei'is arteniisicefolia (Brongn), to which, as identified in our American 

 collections, E. lineolniaua is closely related, or possibly ancestral. 



Although from the habit and mode of division of the tertiary pinnae 

 the fern is apparently referable to the Sphenopteroid division of the 

 genus Eremopteris^ the basal ramification, so far as it can be deter- 

 mined from the specimens ))efore me, imparts a suspicion that the 

 frond of this species, like that from Missouri, maj'' divide in the same 

 manner as the fronds of Diplothmena. As stated in the discussion of 

 the ferns from the Lower Coal Measures of Missouri, I believe l)oth 

 species to have been derived from the Archseopteroid stock through 

 the genus TrlphyUopteris. It seems far from improbable that Erem- 

 opteris^ Rhacopteris^ Anehiiites^ Asplenltes^ Sphcnopjfer/'dium dissect am 

 (Goepp.) Schimp., and S'plienop)tefris excelsa L. and H. are members of 

 an early comprehensive group of Paleozoic ferns. 



This species has not yet l)een found above the top of the Pottsville 

 series, although it appears to occupy a period near the close of that 

 formation, and to be most closely related to an undescribed form in 

 the lower pcn'tion of tht> Kanawha series in West Virginia. The type 

 specimens are from the New Lincoln mine, where its association in 

 the matrix with Xexiropteris Elrodi Lx. renders it nearly certain that 

 it comes from Lykens coal No. 2 or No. 3, probably No. 2. AVith 

 it is also found the E. Lehmanni. E. lincolniana is also present from 

 the Lincoln mine, where it is associated with the same species as at 

 New Lincoln, In the Pottsville Gap the species occurs 550 feet Ixdow 

 the Twin coal; i. c. near the supposed horizon of Lykens coal No. 3. 



Eremopteris Cheathami Lx. 



This plant, described by Lesquereux from Rockwood and Tracy 

 City, TeniH^ssee, is one of the most clearly marked and well differenti- 

 ated fern species of the entire formation. Its nuxst prominent features 



