CYCADITES. 



25 



generic determination. When we come to examine the various 

 plant fragments which have been figured as representatives of 

 the genus at different geological horizons, it becomes apparent 

 that the mere acceptance of a list of Cycadites species as an index 

 of the past history of the genus would undoubtedly lead us into 

 error. In any case it would be rash to maintain that a record 

 of even the most perfectly preserved specimens of the Cycadites 

 type of frond, affords an epitome of the geological history of the 

 genus Cijcas. The occurrence of fossil carpellary leaves very 

 similar to, or practically identical with, those of Cycas, lends 

 confirmation to the position assigned to many of the Cycadites 

 fronds ; but as regards other species we can only express the 

 opinion that they are parts of a plant which closely resembles 

 in habit, and probably in structure, the living genus. It has 

 already been pointed out that the pinnae of Cycas circinalis, L., 

 may occasionally be united laterally and assume a form suggestive, 

 in some degree, of Nilssonia or Pterophyllum. No great weight 

 can be attached to this single instance of such lateral fusion, but 

 it is worth noting as having a possible connection with some 

 of the fossil leaf forms which present little resemblance to 

 recent fronds. Saporta has called attention to the similarity 

 between some Cycadites species and Nilssonia, and one of Heer's 

 species, C. Dichoni 1 from the Cretaceous of Greenland, seems 

 to possess pinnae which are either in contact with one another, 

 or actually united by the margins. 



Berger figured a fragment as Cycadites alatus, Berg., 2 and 

 compared it with Nilssonia brevis, Brong., the same plant being 

 afterwards renamed by Go'ppert Nilssonia, Bergeri.* As regards 

 the first record of Cycadites in Paleozoic rocks, it cannot be said 

 that there is any very decided evidence of the occurrence of this 

 genus, but Gb'ppert's C. taxodinus is by no means such a doubtful 

 representative of the genus as several of the species described 

 from newer beds. Go'ppert' s C. yyrosus may perhaps be a portion 

 of a young frond with its pinna3 circinately rolled, but it is not 

 enough to establish the existence of Cycadites in Carboniferous 

 times. Sterzel has recently figured an imperfectly preserved 



1 Heer (A. 3.), Fl. foss. Arct. vol. iii. pt. ii. p. 99, pis. xxvii. and xxviii. 



2 Berger, p. 22, pi. iii. figs. 5 and 6. 



3 (l),p. 141. 



