24 CYCADITES. 



uninerved and apparently palraately-arranged segments; this he 

 described as probably a Filicite. Brongniart l afterwards referred 

 Mlsson's plant to Cycadites, on account of the resemblance of 

 the leaf segments to the pinnae of the recent genus Cycas. As 

 Schenk 2 has pointed out, Nilsson's figure in all probability 

 represents an Aralia leaf, and the fossil is certainly not a species 

 of Cycadites. In Brongniart's Prodrome* we have the following 

 definition of the genus Cycadites : 



" Feuilles pinnees, a pinnules lineaires, entieres adherentes 

 par toute leur base, traversees par une seule nervure moyenne, 

 epaisse ; point de nervures secondaires." 



He regards the single-veined linear pinnae as the important 

 feature, and in spite of the fact that the first specimen to be 

 included under this generic name was incorrectly determined, 

 this definition of Cycadites has been generally adhered to. 



Schimper, Saporta, and other authors have, in the main, 

 adopted Brongniart's diagnosis. We may perhaps most con- 

 veniently define Cycadites as follows : 



Frond pinnate, pinnaa alternate or opposite, linear, lanceolate, 

 entire, with a single median vein ; attached to the rachis by 

 the entire base, the lower margin of which may be slightly 

 decurrent on the frond axis, or slightly narrowed towards the 

 point of attachment. 



It is better to confine our definition to the frond characters, 

 and thus frame it in such a manner that it practically includes 

 those fossil fronds which have a cycadean habit, and resemble 

 the recent Cycas in the possession of uninerved segments. In 

 several cases Cycadites fronds have been found in close associa- 

 tion with characteristic Cycas-like carpellary leaves ; but in the 

 majority of specimens we have only sterile fronds, and it is 

 better, therefore, to have some definition which enables us to 

 give such leaves a place in a convenient genus, which does not 

 depend upon special characters of fertile leaves. 



The genus Cycadites, as defined by most writers since the 

 days of Brongniart, possesses easily recognized characters, and 

 ought not to present any very serious difficulty in the way of 



1 (A. 2), p. 93. 



2 (A. 1), Fl. foss. Grenz. Keup. p. 158. 



3 p. 93. 



