578 CYCADOPHYTAN FRONDS [CH. 



fronds described as Pterophyllum Morrisianum^ appear to be 

 indistinguishable from this species. 



Nilssonia Schaumburgensis (Dunker). 



This species, first described as Pterophyllum Schaumburgense^ 

 from the Wealden of Germany, afEords a good illustration of a 

 small type of frond closely resembhng the much larger species 

 N. compta. Examples from EngUsh Wealden rocks seldom exceed 

 1 cm. in breadth and are often much narrower ; the linear lamina 

 is almost entire or divided into short and broad truncate segments 

 of unequal breadth: the veins are parallel and simple. For 

 figures of this species, recorded from different European locahties 

 and from Japan, reference should be made to the accounts by 

 Schenk^, Nathorst, Yokoyama, Yabe, and Fontaine. 



CTENIS. Lindley and Hutton. 



The genus Ctenis* was founded on a piece of pinnate frond 

 from the Middle Jurassic rocks of the Yorkshire coast previously 

 figured by Phillips as Gycadites sulcicaulis. Lindley and Hutton 

 regarded the plant as probably Cycadean and proposed to apply 

 the name Ctenis to all leaves having the general characters of 

 Cycadeae, but with 'the veins connected by forks or transverse 

 bars.' While many authors have accepted Ctenis as a Cycadean 

 genus, by others ^ it has been placed among the Ferns, on the 

 ground that some small circular elevations on the lamina of the 

 segments of certain species are believed to be sori or sporangia. 

 Since Ettingshausen* and Schenk' first noticed this feature 

 Raciborski* has figured several examples from Poland and Staub* 

 records similar circular bodies on a Liassic Hungarian, species. 

 In no single instance have sporangia been found. Nathorst^" pro- 

 posed the designation Anthrophyopsis (because of the resemblance 

 of the lamina in form and venation to the leaves of the Fern 



1 Oldham and Morris (63) B. PI. xv. fig. 1. 



" Dunker (46) A. p. 15, PI. i. fig. 7, etc. ; Seward (95) A, p. 53. 

 ' Schenk (71) B.; Nathorst (90) A.; Yokoyama (94); Fontaine in Ward 

 (05) B.; Yabe (13). 



4 Lindley and Hutton (34) A. Pi. out. ; Phillips (29) A. PI. vii. fig. 21. 

 •■ Zeiller (00) B. p. 115; Krasser (09) p. 113. « Ettingahausen (51). 



' Schenk (68^). « Raoiborski (94) A Pis. xvn.— xix. 



' Staub (96). i» Nathorst (86) p. 43. 



