XXXIX] PTILOPHYLLTJM 521 



leaves from Griaham Land included in that genus by Halle^ are 

 in my opinion inseparable from Ptilophyllum, and this applies 

 equally to Otozamites Hislopi (Old.) (iig. 589) and 0. abbreviatus 

 as figured by Feistmantel and by Halle. The nomenclature of 

 Cycadean fronds having the habit of Ptilophyllum pecten is a 

 great difficulty: after carefully reconsidering the whole question 

 and comparing Feistmantel's figured specimens with the large 

 series of English fronds the conclusion reached is that the 

 characters exhibited by ordinary impressions do not admit of 

 any satisfactory grouping imder well-defined specific types. In 

 the first place, as already indicated, the use by some authors of 

 the generic names Ptilophyllum, Otozamites, and Zamites creates 

 a false impression of the degree of difference between the numerous 

 forms of frond agreeing more or less closely with the specimens 

 on which were founded th.e species Ptilophyllum acutifolium, 

 P. cutchense, P. pecten, and P pectinoides (figs. 587, 591, 595, etc.). 

 In his important memoir on the Jurassic flora of Graham Land 

 Halle^ discusses the limitation of Ptilophyllum, Zamites, and 

 Otozamites. He employs Zamites for fronds with linear pinnae 

 attached to the upper face of the rachis by a base which is more 

 or less, but often very little, rounded and always asymmetrical, 

 with or without a basal callosity: fronds of the type Z. gigas 

 he includes in the section Euzamites , while Z. borealis and similar 

 forms (fig. 597) are referred to a second section, Subzamites. It is 

 in the sense of Halle's section Euzamites that the generic name 

 Zamites is employed in this chapter. On the other hand the fronds 

 grouped by Halle as Subzamites have pinnae with the basal angles 

 of the lamina very slightly rounded precisely as in Ptilophyllum 

 as seen in fig. 596 (c/. fig. 598 which represents fronds referred 

 by Halle to Zamites); and they are not distinguished by any 

 feature of generic importance from Ptilophyllum as defined on 

 page 519. The species Zamites pusillus, Z. Anderssoni, and 

 Z. antarcticus (fig. 598) described by Halle from Graham Land 

 as well as Heer's Arctic forms^ Z. borealis (fig. 597), Z. speciosus, 

 Z. brevipennis, and others are transferred to Ptilophyllum as 

 types agreeing very closely with P. pecten and in some cases not 

 clearly distinguishable from it even specifically. 



1 Halle (132). 2 ibid. ^ Heer (75) 11. Pis. xrv.— xvi. 



