FLORA OF THE OOLITIC EPOCH. 



81 



liar forms. Its distinctive characters are, the rarity of Ferns 

 with reticulated venation, which are so numerous in the Lias, the 

 frequency of the Cycadaceous genera Otozamites and Zamites, 

 which are most analogous to those now existing ; the occur- 

 rence of a remarkable group presenting very anomalous struc- 

 ture in their organs of reproduction, to which Carruthers has 

 given the name of Williamsonia ; and the diminution of Ctenis, 

 Pterophyllum, Pal^ozamia, and Nilssonia, genera far removed 





Fig. 81. 



from the living kinds ; and lastly, the greater frequency of 

 the coniferous genera, Brachyphyllum and Thuites, which 

 are much more rare in the Lias. In the Scottish Oolite at 



the Oolite of Scarborough. Lower part of the piunatifid leaf, with 

 bkmt ahnost square divisions. There are numerous veins, slightly 

 varying in thickness ; while in Pterophyllum there are numerous veins 

 of equal thickness, in Cycadites there is a solitary vein forming a thick 

 midrib. Fig. 80. Pakuozamia ijectinata (Zamia xiectinata of Brong- 

 niart, and Lindley and Hutton), a pimiated leaf, with a slender rachis. 

 The pinnae are linear, somewhat obtuse, with slender equal ribs. It 

 is found in the Oolite of Stonesfield (Lindley and Hutton). 



Fig. 81. Brachy2)hyllu7ii mammillare, a Coniferous plant of the 

 Oolitic system, Yorkshire. 



Fig. 82. Equisetum columnare, a fossil opecies of the Oolite of 

 Yorkshire. 



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