582 CYCADOPHYTAN FRONDS [CH. 



and other examples of large Ctenis fronds are described by Raci- 

 borski from Lower Jurassic rocks in Poland. He figures part 

 of a leaf of C. Zeyschneri^ 40 cm. long bearing alternate pinnae 

 approximately 10 cm. long and nearly 4 cm. broad, characterised 

 by obtuse apices, a decurrent lamina, and anastomosing veins 

 closer together (16 — 24 per 1 cm.) than those of C. asplenioides. 

 In one Polish specimen, C. remotinervis^, with pinnae 5 cm. 

 broad the lamina is represented in the upper part of the frond as 

 continuous over the face of the rachis, and — if th^ drawing is 

 accurate — the frond in this respect differs from typical examples 

 of Ctenis and agrees with Nilssonia. A species of Ctenis with 

 broad pinnae is described by Yokoyama* from the Jurassic of 

 China as C. Kaneharai. 



Ctenis sulcicaulis (PhiUips). 



This type* is more famiUar under the name Ctenis falcata 

 given to it by Lindley^, but if we follow Lester Ward* in strict 

 observance of the rule of priority, a course from which I have 

 frequently deviated on the ground of long usage, the less familiar 

 designation must be adopted. Fronds pinnate ; long and tapered 

 linear pinnae sometimes exceeding 12 cm. in length and 1 cm. in 

 breadth attached obliquely or almost at right-angles to a fairly 

 broad rachis (fig. 626). The lamina is broadest at the base and the 

 lower margin is strongly decurrent, tapering distally to an acute 

 apex. The parallel and frequently anastomosing veins diverge 

 sHghtly in the basal region of the pinnae. Though usually separate 

 to the base, the laminae of adjacent pinnae may be continuous 

 as in a pinnatisect leaf. This species is recorded also from 

 North America, and fronds of similar habit are figured by Fontaine^ 

 from the Jurassic of Oregon as Ctenis orovillensis : a fragment 

 recorded from Jurassic rocks in Afghanistan as Ctenis sp. may 

 belong to C. sulcicaulis^. 



' Raciborski (92) PI. ii. fig. 2. 



2 Ibid. (94) A. PI. xvni. fig. 2. » Yokoyama (06) B. PI. ix. 



4 Phillips (29) A. p. 148, PI. vn. fig. 21. " Lindley and Hutton (34) A. PI. cm 



" Ward (06) B. p. 113. 



' Seward (00) B. p. 235, PI. vni. fig. 2 ; Zigno (56) A. PI. xxiv. 



* Fontaine in Ward (05) B. Pis. xxvn. — xxviii. 



» Seward (12) PI. iii. fig. 43. 



