132 Reviews — The Jurassic Rocks of England. 



possible that the Abhotsbury Ironstone is on the horizon of the 

 " Pterocerian " beds, though the .P/eroceras-fauna is wanting in this 

 country. 



There can be no doubt that the Corallian series as developed at 

 Weymouth and Osmington presents many attractions, both to tbe 

 stratigraphist and the collector. It is so varied, so accessible, and 

 so fossiliferous, and there are such excellent sections on tbe coast, 

 that the geologist is invited, as it were, to bring out his hammer, 

 his compass, and his tape, and try what he can make of the 

 exposures. The very fact of the whole series occurring in duplicate, 

 i.e. on either siile of the Weymouth anticline, renders the study of 

 these rocks all the more interesting. Mr. Woodward's measure- 

 ments differ somewhat from those of Blake and Hudleston, but in all 

 other respects he confirms their work. An ample list of fossils from 

 the Corallian rocks near Weymouth, including the Abhotsbury iron- 

 ore, concludes this part of the subject. 



Full details of the Corallian beds are given as they are traced 

 towards the north-east, until their final disappearance in a distinct 

 lithological form in Oxfordshire. The subject of the Ampthill Clay 

 may detain us for a moment. Although this argillaceous equivalent 

 of Corallian beds was first indicated by Prof. Seeley, it is to the 

 labours of the late Thomas Roberts that we owe most of our know- 

 ledge of its contents. The subject, like that of all Fen clays, is a 

 difficult one, and distasteful to many ; but Roberts' singular know- 

 ledge of Upper Jurassic fossils enabled him to grapple with it 

 successfully, and the readers of the Quarterly Journal may remember 

 that he ventured to map this Corallian clay in Cambridgeshire and 

 Lincolnshire. 



Kimeridge Clay (Kimeridgian). — The term "Kimeridge strata," we 

 are told, was employed in 1812 by Thomas Webster, and in 1818 

 the term "Kimeridge Clay" was used by Buckland. In England 

 the beds of this age are mainly clays. When we bear in mind 

 that this formation varies in thickness from 1200 feet in the great 

 Kimeridgian trough of the south of England to less than 100 feet in 

 the neighbourhood of Oxford, and that it includes a variety of zones 

 recognized on the Continent, some based on Cephalopoda and others 

 on different orders of Mollusca, it must be admitted that an author 

 in Mr. Woodward's situation has unusual difficulties to contend with. 

 There is even a further trouble, viz. how to distinguish between 

 Kimeridgian clays and Portlandian clays, in cases such as Hartwell, 

 where no lithological indications of a separation between the two 

 present themselves. To show such a Portlandian clay on a map 

 would be next to impossible : indeed, the only place in England 

 where a palpable Portlandian clay is clearly separated from the 

 Kimeridge Clay by beds whose fauna and lithology are distinct, 

 occurs at Swindon. 



Agreeing with Prof. Blake that there is no need in this country 

 to divide the Kimeridge Clay into more than two zones for general 

 stratigraphical purposes, Mr. Woodward adopts the following 

 arrangement (see table on page 133) : — 



