310 CONCLUSION. 



fossils among the Yorkshire plants which afford sufficiently good 

 evidence to warrant their inclusion in these families; it is possible 

 that Tceniopteris vittata, which is one of the commonest species, 

 may belong to the Marattiaceae, and it may be that some of the 

 Sphenopteroid fronds possessed Hymenophyllaceous soral characters. 



It is among the ferns of the Southern Hemisphere that we find the 

 closest resemblances to the Inferior Oolite species. The Malayan 

 species Matonia pectinata is essentially a Jurassic and Lower 

 Cretaceous type ; the Indian and Malayan Bipteris recalls Dicfgo- 

 phyllum rugosum. Thyrsopteris elegans of Juan Fernandez, Bicksonia 

 arborescens of St. Helena, Balantium culcita of Madeira and the 

 Azores may be cited as Cyatheaceous types most nearly allied to 

 those of Jurassic age. Todea Barbara, a native of New Zealand 

 and tropical Australia, is the nearest living representative of 

 Todites Williamsoni. The Schizaeaceae are to-day widely distributed 

 in both hemispheres, but several members of the family are 

 characteristic of Southern latitudes. 



Glnkgoales. The two genera Ginkgo and Baiera, although both 

 appear to have been in existence in the Triassic and even Permian 

 periods, are essentially characteristic of Bhaetic and Jurassic floras. 

 The Inferior Oolite species of Baiera are very similar to Bhaetic 

 forms, while Ginkgo digitata is for the most part a Jurassic and 

 Cretaceous type of wide geographical range. The trees, which 

 bore the Ginkgo and Baiera foliage, and flowers, which were 

 probably rather more Cycadean in structure than those of the 

 recent Maidenhair- tree, must have formed a striking feature in 

 the Jurassic vegetation. The extreme northern range of Baiera 

 and Ginkgo points to a vigorous development of the Ginkgoales 

 during the latter part of the Mesozoic era. 



Cycadaxes. At no period in the earth's history were the 

 Cycadaceae more abundantly represented than in Jurassic times. 

 Williamsonia, Nilssonia, and Otozamites are the most conspicuous 

 examples of the Cycadales in the Yorkshire flora; Williamsonia 

 gigas may be compared with the English Wealden type W. 

 Carruthersi ; Williamsonia pecten is one of the most abundant and 

 at the same time one of the most characteristic of the Inferior 

 Oolite species. The Bennettiteae appear to have attained their 

 maximum development in the Upper Jurassic and Lower Cretaceous 

 periods ; the two species Williamsonia gigas and W. pecten are 

 typical Jurassic types, and Anomozamites Nihsoni recalls the Bhaetic 



