THE GEOLOGICAL MIDDLE AGE. 
169 
the C6te d’Or. With this latter upheaval began 
the Cretaceous epoch, which we will examine 
with special reference to its subdivision into peri- 
ods, since the periods in this epoch have been 
clearly distinguished, and investigated with espe- 
cial care. I have alluded in the preceding article 
to the immediate contact of the Jurassic and Cre- 
taceous epochs in Switzerland, affording peculiar 
facilities for the direct comparison of their or- 
ganic remains. But the Cretaceous deposits are 
well known, not only in this inland sea of ancient 
Switzerland, but in a number of European basins, 
in France, in the Pyrenees, on the Mediterrane- 
an shores, and also in Syria, Egypt, India, and 
Southern Africa, as well as on our own continent. 
In all these localities, the Cretaceous remains, 
like those of the Jurassic epoch, have one organic 
character, distinct and unique. This fact is espe- 
cially significant, because the contact of their 
respective deposits is in many localities so imme- 
diate and continuous that it affords an admirable 
test for the development-theory. If this is the 
true mode of origin of animals, those of the later 
Jurassic beds must be the progenitors of those of 
the earlier Cretaceous deposits. Let us see now 
how far this agrees with our knowledge of the 
physiological laws of development. 
Take first the class of Fishes. We have seen 
that in the Jurassic periods there were none of 
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