262 Antediluviafi Zoology and Botany. 



practices of the vulgar, and in return for the pains I take 

 to cater for your information, you must occasionally allow me 

 to digress, and indulge my own peculiar humour. 



I am. Sir, &c. 



G. J. 



Art. XII. Illustrations of Antediluvian Zoology and Botany, 

 By R. C. Taylor, Esq. F.G.S. 



{Continued from p. 78.) 



One of the principal objects of geology is to distinguish 

 the different epochs which have succeeded each other during 

 the formation of the globe. This is best effected by means 

 of the organic remains contained within the strata. 



Mineralogical characters are found to vary so frequently, 

 while zoological analogies are comparatively so constant in the 

 same epochs or formations, that geologists feel assured of the 

 superior value of these latter tests. " In those cases, where 

 characters derived from the nature of the rocks are opposed 

 to those which we derive from organic remains, I should 

 give," M. Brongniart remarks, " the preponderance to the 

 latter." * 



In tracing any of our best recognised English formations, 

 we cannot but be struck with the applicability of this rea- 

 soning. At the same time it would be too much to expect the 

 complete identity, the perfect similarity, of these and other 

 formations, at remote points, without occasional zoological as 

 well as mineralogical deviations from that which we have been 

 accustomed to consider the type. All formations possess local 

 modifications. We might instance, as most familiar to us, 

 the variations in the zoological characters of the London clay, 

 at several points where sections are exposed. Thus at Har- 

 wich, at Sheppy, at Bognor, Stubbington, and Barton, are 

 deposits of Testacea, which may, so far as we know, be almost 

 local. The plastic clay has equally local accumulations of 

 shells. Nor is the circumstance at all remarkable ; for it is 

 repeated in the beds of living shellfish, and marine exuviae, 

 upon our present coasts ; and no one acquainted with the 

 gregarious habits of this part of the creation would look for 

 an equal distribution of their remains, either on our shores 

 or in their fossil state. 



It is proposed to comprise within the limits of the present 

 and a succeeding article, an outline of the principal depart- 



* Address to the Academy of Sciences On the Importance of Zoological 

 Characters in Geology ^ by M. Brongniart. 



