FEENS— MBGALOPTEEIDB.E— NEUEOPTERIS. 135 



short, when deahng with specimens from the Lower Productive Coal Meas- 

 m-es, though when but a few specimens are in hand it is frequently pos- 

 sible to separate them into two groups according to a single character, 

 such a division, when the series is large or a number of localities of close 

 stratigraphic relation are represented, is usnalh' difficult, if not wholly 

 impossible. 



Concerning the name to be employed for this species there is still slight 

 uncertainty. Although the specimens from the United States agree well 

 with material in the Lacoe collection from Cape Breton, Nova Scotia, and 

 the Bristol coal field in England, and are no doubt the same species, I am 

 not now fully assured that they are specifically identical with the more 

 triangular pinnules from the Valenciennes Basin, published by Professor 

 Zeiller; and accordingly, if Zeiller's form is certainly the same as that poorly 

 described and illustrated by Hoffman, it seems probable that the type, with 

 broader and more lingulate pinnules, might deserve an independent specific 

 designation, in which case Lesquereux's name, N. hirsuta, would have pri- 

 ority. The examination and publication of additional specimens from 

 Hoffman's locality is much to be desired. 



With regard to variation in a species, Neuropteris Schetichzeri is one of 

 the most interesting of American "Paleozoic ferns. Ranging, as it does, from 

 near the base of the Lower Productive Coal Measures, or Alleghany series, 

 to the highest plant beds of the "Permian" or Dunkard Creek series, it 

 presents a valuable illustration of the modification of a species found at 

 many horizons in a thick series of probably continuously deposited sediments. 

 So far as my observations have extended in collections from American 

 localities and horizons, it may be noted that, in general, both in the anthra- 

 cite and in the bituminous fields, the earliest representatives of the species, 

 in the lowest coals, are prevaihngly smaller, narrower, and more ti-iangular 

 and pointed, the hairs fine, short, and often invisible. A little higher, as, 

 for example, in the E or F veins, as numbered in the northern anthracite 

 field by the Pennsylvania geological survey, the narrow, acute forms 

 become rare and the proportion of broader, more obtuse pinnules increases, 

 the pinnules becoming large at the same time and more conspicuously hir- 

 sute, while at the horizon of the Pittsburg coal and of the higher anthracite 

 coals the leaflets are mostly broad and lingulate, the hairs less plain ; and 



