1 8 STUDIES IN GEOLOGY, No. 4 



the Asplenites elegans of Ettingshausen, a species often re- 

 ferred to Eremopteris. This latter is a form characteristic 

 of the Westphalian stage and the fact that the later described 

 species referred to Rlhacopteris are especially characteristic 

 of the Culm (Dinantian and Mississippian) and some of 

 them approach Archaeopteris in form and venation, has 

 resulted in giving the name Rhacopteris a chronologic signif- 

 icance which obscures rather than elucidates the floral his- 

 tory of the Carboniferous. 



Rhacopteris was characterized as having simply pinnate 

 forked fronds with trapezoid or rhomboid pinnules with 

 lobed margins, and is supposed to be more typical of the 

 Lower (Culm,) than of the Upper (Pennsylvanian) Carbon- 

 iferous. I know of no evidence to indicate that the supposed 

 Rhacopteris frond is other than a single pinna of an Eremop- 

 teris frond. Most of the attempts at a systematic arrange- 

 ment are highly artificial, notably that of Potonie as elabor- 

 ated in Engler and Prantl. The truth is that our informa- 

 tion is as yet too incomplete to permit of a satisfactory delim- 

 itation of the overlapping generic terms now in use. 



Lesquereux, in his study of American Carboniferous floras 

 used Eremopteris in a rather broad way and in this he was 

 followed by White. I regard this as the most logical treat- 

 ment and consider Eremopteris as suitable for most of the 

 series of forms, largely intermediate in both form and chron- 

 ologic occurrence between Triphyllopteris and Mariopteris. 

 For example the present Hremopteris peruianus is very sim- 

 ilar to the Rhacopteris tramitionis (Ettingshausen) Stur 

 from the Upper Culm of Moravia. It is almost equally close 

 to Hremopteris crenulata Lesquereux from the Westphalian 

 of Alabama. The second species of Eremopteris enumerated 

 by Schimper, namely, . Neesii came from the Bohemian 

 Permian and Zeiller subsequently transferred it to Callipteris. 



