Ill] 



JURASSIC EOCKS. 



49 



and shales, we have remnants of an exceedingly rich and appa- 

 rently tropical vegetation. This was an age of Reptiles as well 

 as an age of Cycads. An interesting feature of these widely 

 distributed Jurassic strata is the evidence they afford of distinct 

 climatal zones ; there are clear indications, according to the late 

 Dr Neumayr, of a Mediterranean, a middle European, and a 

 Boreal or Russian province^. The subdivisions of- the English 

 Jurassic rocks are as follows^ : — 



Jurassic 



Purbeck beds \ 



Portland beds i Upper 



Kimeridge clay J 



Corallian beds \ 



Oxford clay, with [ Middle 



^ Kellaways rock J 



(Great Oolite series 1 

 (Inferior Oolite series ] 



Lias 



y Oolite. 



In tracing the several groups across England, and into other 

 parts of Europe, their characters are naturally found to vary 

 considerably ; in one area a series is made up of typical clear 

 water or comparatively deep sea sediments, and in another we 

 have shallow water and shore deposits of the same age. The 

 Lias rocks have been further subdivided into zones by means 

 of the species of Ammonites which form so characteristic a 

 feature of the Jurassic fauna. In the lower Oolite strata there 

 are shelly limestones, clays, sandstones, and beds of lignite and 

 ironstone. Without discussing the other subdivisions of the 

 Jurassic period, we may note that in the uppermost members 

 there are preserved patches of old surface-soils exposed in the 

 face of the cliffs of the Dorset coast and of the Isle of Portland. 



' Neumayr (83). 



2 Woodward, H. B. (87), p. 255. 



