FERNS— EESTRICTION OF GENUS PSEUDOPECOPTBRIS. 23 



frond divisions of Mariopteris, thus leaving- no good reason for the con- 

 tinuance of the former genus. So far as I am aware, however, this mode 

 of .division has not yet been seen in the group represented by Pseudopecop- 

 teris oUusUoba or Ps. anceps Lx. (Sphenopteris neiiropteroides Boulay), wliich 

 is still included by most European authors in the genus Sphenopteris, 

 although it is generally recognized as distinct from the true Sphenopterids. 

 This group is one of considerable solidarity, the line of demarcation 

 l^etween it and the other species of Sphenopteris being fully as distinct as 

 that between mau}^ of the familiar genera resting on the superficial char- 

 acters of the sterile fronds in the Carboniferous flora. For tliis reason, 

 which was largely the cause of its inclusion by Lesquereux in the genus 

 Pseudopecopteris, I would, after removing those species which conform to 

 the older genus Mariopteris, propose to restrict the genus Pseudopjecopteris 

 to the very natural group of large-round-pinnuled species^ ty^jically repre- 

 sented by the Sphenopteris oUusiloba of Brongniart. 



Although these generic divisions are artificial, and the species now 

 associated in a genus may eventually be found to belong to entirely differ- 

 ent orders, I believe that the interests of the study of the Carboniferous 

 flora will be promoted by the maintenance of the genera Mariopteris and 

 Pseudopecopteris, as above restricted, Diplothmema being reserved for the 

 group of dissected forms, of which D. furcatum (Brongn.) Stur is a typical 

 example. In this classification Mariopteris Zeill. includes the Pecopteroid 

 or Alethopteroid forms, in which the piimary pinnae are divided by a double 

 dichotomy into four di^dsions of equal rank, while Pseudopecopteris may 

 comprise the round-lobed or round-pinnuled^ species of the type of Sp)he- 

 nopteris oUusiloha- Brongn. The fronds of this type, to which among others 

 1 would refer S. Schillingsii Andra, S. solida Lx., and S. neiiropteroides Boulay, 

 are perhaps dichotomous in the lower part, though a quadripartite habit 

 has not, I believe, been observed. 



'The relations of several species, lite Ps. Sheaferi Lx., placed in the section "Gleichenites" 

 by Lesquereux, but the relation of which to the ohtusiloba group seems very distant, if observable, 

 can best be treated in a revision in detail of the material included in the genus Pseudopecopteris. 



2 Section "Neuropteroides" of Brongniart, in part. 



