512 CYCADOPHYTAN FRONDS [CH. 



than the Bennettitales to modem Cycads. Until definite evidence 

 is obtained as to the nature of the reproductive organs of Nilssonia, 

 Ctenis, and Ctenopteris it is impossible to say how closely these 

 genera agree in essential characters with existing members of the 

 Cycadales. If, as has been suggested, the fertile shoots known 

 as Beania 1 belong to Nilssonia their resemblance in plan of con- 

 struction to the cones of recent genera, much greater than in the 

 case of the flowers of the Bennettitales, is in accordance with the 

 evidence of the epidermal characters. 



Reference was made in the second Volume of this book to 

 several genera founded on fronds which through lack of evidence 

 as to the nature of the reproductive organs cannot be assigned 

 with certainty either to Ferns or Cycads: it was stated that 

 the genera Ptilozamites and Ctenopteris are probably Cycadean, 

 and the structure of the epidermal cells in the latter genus lends 

 support to this view 2 . Among other genera of doubtful position 

 not included in the following descriptions of fronds is Zamiopsis 

 of Fontaine 3 founded on large compound fronds from the Potomac 

 formation: the venation and form of the pinnae are more Fern- 

 like than in Ctenopteris, but in general habit the two genera are 

 not very dissimilar. The generic name Zamiopsis is misleading 

 as the species bear no resemblance to Zamia or Zamites. 



I. BENNETTITALES. 

 PTILOPHYLLUM. Morris. 



The generic name Ptilophyllum was instituted in 1840 for 

 some specimens of pinnate fronds from Cutch: in this genus 

 Morris 4 included with the Indian leaves the English Jurassic 

 species Pterophyllum pecten Lind. and Hutt. 5 (figs. 587, etc.) and 

 some other forms. He defined Ptilophyllum as follows : ' Fronds 

 pinnate; pinnae closely approximated, linear, lanceolate, more 

 or less elongate, imbricate at the base, attached obliquely; base 

 semicircular or rounded; veins equal, slender, parallel.' Morris 

 adds that he instituted a new genus in preference to Zamites 



1 See page 502. 



2 Nathorst (08) PI. i. figs. 3- 5 ; Thomas and Bancroft (13) p. 194, PI. xx. fig. 12. 



3 Fontaine (89) B. p. 160, Pis. LXI. LXVI. ; Berry (11) p. 354. 



4 Morris (40) PL xxi. figs. 14. 5 Lindley and Button (34) A. PL en. 



