Vol. 69.] THE CLEVELAND DISTRICT OF YORKSHIRE. 247 



V. Summary and Conclusion. 



The classic researches of the last century on the Jurassic flora of 

 Yorkshire were based on collections made from localities lying for 

 the most part between Whitby and Piley ; in the present paper the 

 description of plants from localities on the northern side of the 

 Cleveland Hills is commenced. The beds from which these plants 

 have been obtained belong to the Lower Estuarine Series of the 

 Middle Jurassic, but the flora differs considerably from that seen in 

 the more southern localities. It differs both in its component 

 species and in their relative abundance. 



Several forms occur at Marske which have not been recorded 

 from other localities in Yorkshire, or, in fact, from elsewhere in 

 England. These are Marattiopsis anglica, Dictyozamites hawelli, 

 Pseudoctenis lanei, and Baiera longifolia. The Baiera has been 

 irecorded from other localities in Europe and Asia, but the remainder 

 of these species are regarded as new to science. Stacliypteris 

 hallei has been found at Marske, and only one other specimen is 

 known from near Whitby. 



The dominant plants at Marske are undoubtedly Ptilopliylla 

 ( Williamsonice) of the pecten type. The fronds of this form are 

 numerous, but have not yet been examined critically. Male and 

 female Williamsonia flowers also occur. Tceniopteris vittata, too, is 

 very abundant. Baiera longifolia, Nilssonia mediana, and Dictyo- 

 zamites haivelli are abundant. Sagenopteris phillipsi is locally 

 plentiful. The ferns do not occur so frequently : Marattiopsis 

 ,anf/lica and Coniopteris hymenopJiylloidcs are probably the most 

 plentiful, but the former is not so abundant as at lloseberry 

 Topping, where it is one of the dominant plants. Todites, Dictyo- 

 phyllum, and Laccopteris appear to be rare. 



In many localities the different beds are usually characterized by 

 different plants. Since only three beds, separated one from the other 

 by only 10 to 15 feet, have been examined at Marske, it may be as 

 yet unwise to compare this flora with that of the localities already 

 known. It may be noted, however, that while the plants here 

 described resemble those from the neighbourhood of Whitby in the 

 abundance of fronds of PtilopliyUum ( Williamsonia) pecten and some 

 other types, yet the flora lacks the plentiful Coniopteris and Brachy- 

 phyllum found in the latter locality. On the other hand, Nilssonia 

 mediana and Sagenopteris phillipsi are infrequent at Whitby, but 

 plentiful at Gristhorpe in the Middle Estuarine Series. So far as 

 has been noted, the flora from Roseberry Topping 1 is still more un- 

 like that of the southern localities, although possessing close affinities 

 to that of Marske. The detailed comparison and analysis of the 

 floras of the various Yorkshire plant-beds will be made later, when 

 the beds on the northern outcrop have been thoroughly examined. 



Dictyozamites haivelli, one of the plants peculiar to Marske, is 

 closely allied to D. johnstrupi from the Lower Jurassic, or possibly 



1 [Since this was written further investigation has emphasized this dis- 

 similarity : see Thomas (13) p. 198.] 



Q. J. G. S. No. 274. s 



