558 CYCADOPHYTAN FRONDS [CH. 



Pterophyllum (Anomozamites) Nilssoni (Phillips). 



The type-specimen, from the Jurassic beds on the Yorkshire 

 coast and now in the York Museum, was described by Phillips 1 

 as Aspleniopteris Nilssoni and placed in Pterophyllum by Lindley 

 and Hutton and many other authors 2 . The fronds are linear; 

 the lamina may be almost entire or divided into unequal deep 

 truncate segments ; the veins are simple or dichotomously branched 

 (fig. 615). The leaves are very similar to those of Nilssonia] 

 they were probably borne on stems similar to those described 

 by Nathorst as Wielandiella. Reference is made to the structure 

 of the epidermal cells in the account of the genus. 



Pterophyllum (Anomozamites) Lyellianum (Dunker). 



This Wealden species, originally referred by Dunker 3 to 

 Pterophyllum, was afterwards transferred to Anomozamites 4 '. The 

 fronds, in habit resembling the larger Rhaetic species P. Braunianum 

 Goepp.,are characterised by the narrow linear pinnae of almost equal 

 breadth attached approximately at right angles ; there is a narrow 

 line of rachis separating the two rows of segments (fig. 616). 



CYCADITES. Sternberg. 



PSEUDOCYCAS. Nathorst. 



The generic name Cycadites was first used by Sternberg 5 

 though it has since been shown that the specimens for which he 

 proposed it belong to other genera. As employed by Brongniart 6 

 and other authors Cycadites stands for fossil fronds agreeing in 

 habit with the pinnate leaves of recent species of Cycas (fig. 387, A) ; 

 the presence of a single median in the linear pinnae is generally 

 regarded as an essential feature. Cycadites may be defined as 

 follows : Fronds pinnate ; pinnae alternate or opposite, linear 

 entire, with a midrib and no lateral veins, attached to the rachis 

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

 decurrent or narrowed near the point of attachment. Epidermal 

 cells with straight walls and stomata agreeing in structure with 



Phillips (29) A. PI. vm. fig. 4. 2 See Seward (00) B. p. 204. 



Dunker (46) A. p. 14, PI. vi. figs. 1, 2. 

 Seward (95) A. p. 91; see also Schenk (71) PL xxxiv. 

 Sternberg (25) A. p. xxxn. 



Brongniart (28) A. p. 93. Specimens named by Brongniart Cycadites 

 Nilssoniana are probably fragments of Dicotyledonous leaves [Nathorst (81) p. 83]. 



