262 Antediluvian Zoology and Botany. 
practices of the vulgar, and in return for the pains I take 
to cater for your iafenention: you must occasionally allow me 
to digress, and indulge my own peculiar humour. 
I an, Sir, &Xc. 
GJ. 
Art. XII. Lllustrations of Antediluvian Zoology and Botany. 
By R. C. Taytor, 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 for mations, 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 
ie af 
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 secamulstons of 
shells. Nor is the circumstance at all remarkable; for it is 
repeated in the beds of living shellfish, and marine exuvie, 
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. 
