XXXIX] PALAEOZOIC FRONDS 509 



in the latter part of the Jurassic period and in the earliest phase 

 of the Cretaceous epoch. In Triassic floras Cycadean plants 

 are represented almost solely by fronds but the very close resem- 

 blance between Keuper species and forms that in Jurassic rocks 

 are foimd in association with fertile shoots leaves little doubt 

 as to the affinity of Keuper and Rhaetic species. 



The evidence obtained from Permo-Carboniferous strata is 

 much more meagre, at least as regards Cycadean leaves: the 

 occurrence of certain morphological Cycadean features is revealed 

 by petrified vegetative organs of Palaeozoic plants, and the 

 Cycadean plan of organisation is conspicuous in many Carboni- 

 ferous and Permian seeds. The discovery of frond-impressions 

 identical in external characters with Mesozoic genera may be 

 accepted as a substantial indication that genera already existed 

 possessing fohage of the Cycadean type, though we have no certain 

 information with regard to the nature of the other organs of the 

 parent- plants. A few examples of Palaeozoic species are included 

 among those selected in illustration of the different genera, 

 namely Plagiozamites Planchardi, Sphenozamites Rochei, Ptero- 

 phyllum Fayoli, P. Cambryi: among other recorded instances of 

 Palaeozoic species are Pterophyllum Cottaeanum Gutb.^, a Permian 

 type similar in habit to Ctenis but without anastomosing veins, 

 a featiire in which it resembles Pseudoctenis; the Carboniferous 

 species Pterophyllum inflexum Eich.^ from the Altai moim tains, 

 transferred by ZeiUer to Dioonites; P. hlechnoides Sand.^ from 

 the Stephanian of Oppenau; Pterophyllum Grand' Euryanum* 

 from Upper Carboniferous beds in France, and P gonorrachis 

 Goepp.^ from Silesia. An examination of the type-specimens 

 of the Carboniferous species Cycadites gyrosus Goepp. and C. taxo- 

 dinus Goepp.® in the Breslau Museum led me to regard the material 

 as too imperfect to determine. 



A conclusion that is forced upon us by a consideration of the 

 geological range of Cycadean fronds is that at the close of the 



1 Gutbier (49) PI. vm. fig. 7. For a fuller account of Palaeozoic records, see 

 Seward (95) A. p. 9. 



3 Eichwald (55) Vol. i. PI. xv. figs. 5, 6; Zeiller (96) A. p. 474. 



3 Sandberger (64) PL n. figs. 1-^. 



« Saporta and Marlon (85) p. 109; Zeiller (06) B. p. 194. 



5 Goeppert (44) PL i. fig. 6. « Ibid. (66) PL u. 



