44 DIOONITES. 



portion of a frond of Dioonites Dunker ianus. The evidence of the 

 figures of Rb'mer and Dunker does not, however, sufficiently 

 support this view to justify our following Schenk's example 

 without having examined the type specimen. In the case of 

 Cycadites Morrisianus, Dunk., there can be little doubt that the 

 specimens referred by Dunker to Cycadites must be transferred 

 to the genus Dioonites. 



It should be pointed out that Ettingshausen had previously 

 suggested the specific identity of Cycadites Morrisianus, Dunk., 

 and Pterophyllum Dunker ianum, Gb'pp. ; he considered it possible 

 that P. Goppertianum ought to be included with these two species. 1 



The specimen figured by Ettingshausen as Cycadites Brongniarti, 

 Rom., 2 has since been placed by Schenk in a new species 

 Cycadites Heerii. 3 



Among the Ecclesbourne specimens there are several good 

 examples which must be included in Go'ppert's species. At first 

 sight many of them would be referred to Cycadites, and the general 

 habit of the frond shows a striking resemblance to that of Cycadites 

 Saporta, sp. nov., but a closer examination demonstrates that no 

 true midrib can be detected, and that the ridge in some of the 

 pinna? which closely simulates such a central vein, is merely 

 the strongly marked convexity of the upper surface of the 

 leaf segments. Among recent cycads the genus Encephalartos 

 affords examples of fronds in which the general habit is strikingly 

 similar to that of Dioonites Dunlcerianus : E. Gliellmcldi, Lem., as 

 shown in PI. XIII. Tigs. 3-5, possesses pinnae of about the same 

 size, and with a very similar mode of attachment, at least as 

 regards their almost horizontal position, but in the lateral insertion 

 to the rachis the segments of the recent species differ from those 

 of the fossil frond. In E. Ghellinckii the convex upper surface 

 of the pinnaB presents a very similar appearance to that in the 

 "Wealden frond segments, and the sharply acuminate tips of the 

 pinnaa is practically identical in the two cases. In PI. XIII. 

 Fig. 3 a portion of a frond of this species is represented, natural 

 size ; in Fig. 4 the median groove on the under side of a single 



' (A. 4), p. 21. 



2 Ettingshausen, loc. cit. p. 20, pi. i. fig. 9. 



3 Schenk (A. 3), Paloeontographica, vol. xix. p. 7, pi. iii. fig. 4. 



