18 CYCADACEJE. 



fronds, such as E. Ca/er, Miq., and other species with broad 

 stout pinna?, one frequently notices that the basal portions of 

 the segments have been depressed in such a way as to present 

 in surface view the appearance of a distinct auriculate base. 

 In some of the examples of Otozamites Klipsteinii (Dunk.) 

 var. superba, described in the present volume, this has probably 

 been the case ; but, thanks to the large number of excellent 

 specimens in the Rufford Collection, it is perfectly clear that 

 the pinnae of this striking plant possessed auriculate bases. 

 The absence or presence of a callosity is often a question of 

 considerable uncertainty among fossil leaves, and the existence 

 of a basal thickening, often none too distinct in the segments of 

 recent species, can only be satisfactorily made out in exceedingly 

 well-preserved specimens. In some cases there is a distinct 

 wrinkling of the coaly surface layer in the position where a 

 callosity would naturally occur, and this may no doubt have 

 sometimes resulted from a callosity in the living pinna, but in 

 others the same appearance may be due to mere bending of the 

 frond segments in the process of fossilization. 



It has been shown by more than one writer how easily the 

 manner of attachment of the pinnae to the rachis may be obscured 

 by the frond being seen from its under side. In the case of Dioon 

 a view of the upper face of the leaf would lead one to refer it 

 to such a genus as Dioonites ; but if the lower surface were 

 exposed to view Pterophyttum would be the most appropriate 

 genus. In a species like Macrozamia Denisoni, Moor and Meull., 

 in which the pinnae are attached along a median line on the 

 upper face of the rachis, the same pinnae seen from below are 

 apparently inserted laterally on the axis, and show no signs of 

 decurrent bases. Braun's figures of Zamites (= Otozamites} brevi- 

 folius, Braun, 1 as seen from above and below, bring out very 

 clearly the striking contrast between the two views ; the same 

 kind of difference is well shown in Feistmantel's figures of 

 Ptilophyttum acutifulium var. maximum, from the Rajmahal Hills 

 of India. 3 



The comparative breadth of the pinna base is a character which 

 varies considerably according to the position of the segment on 



1 PI. xiii. figs. 13-15. 



2 Feistmantel, Pal. lud. pt. ii. pi. xl. 



