Fossil Organic Remains .• %5 
each other ? I am of opinion that this would be pushing the 
induction too far ; and even M. Brongniart, who was so well ac- 
quainted with the value of zoological characters, has limited 
their absolute application to cases where the superposition (the 
circumstances of relative situation) do not oppose it. I might 
mention the cerithia of the coarse limestone, which occur (near 
Caen) beneath the chalk, and which seem, like the repetition of 
the clays with lignites above and below the chalk, to shew a certain 
connection between formations which at first sight might be con- 
sidered entirely distinct. I might adduce other species of shells, 
which belong at once to several tertiary formations, and observe, 
that should species, which at the present day are believed to be 
identical, be separated at some future time by means of charac- 
ters not readily observable, and by slight shades of difference,, 
even the delicacy of these distinctions would not prove too great 
an inducement to believe in the universality, otherwise so desi- 
rable, of zoological characters in geognosy. Another objection, 
taken from the influence exercised by climate even upon the 
pelagic animals, appears to me more important still. Although 
the seas, from well-known physical causes, present at great 
depths the same temperature under the equator and in the tem- 
perate zone, we find, however, that, in the present state of our 
planet, the shells of the Tropics (among which the univalves 
predominate, as among the fossil testacea) differ much from 
those of the temperate climates. The greater number of these 
animals live upon reefs and shoals ; whence it follows that the 
specific differences are often very sensible, under the same paral- 
lel, on opposite coasts. Now, were the same formations repeated 
and extended, so to speak, to prodigious distances, from east to 
west, and from north to south, from one hemisphere to the other, 
is it not probable, whatever may have been the complicated 
causes of the ancient temperature of our globe, that variations 
of climate have modified, in ancient times as at the present, the 
types of organisation, and that one and the same formation 
(that is to say, a rock of the same nature placed, in the two 
hemispheres, between homogeneous formations) may have en- 
veloped distinct species ? It no doubt often happens, that super- 
imposed beds present a very striking contrast of fossil bodies ; 
but should it be concluded from this, that, after a deposit was 
