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ant groups. But this law, though sound as a general expression of 
results, must not be applied too minutely. The Nautilus and the 
Terebratula, the companions of the most ancient form of cephalopodous 
and brachiopodous mollusca, are still represented by existing species ; 
and associated with the pachyderms of the earliest tertiary period, we 
find bats and small carnivora, which can hardly be distinguished from 
animals of the same kind now living. 
“The comparison of the faunas of different epochs shows that the 
temperature of the earth’s surface has undergone change. 
‘“‘ This appears from the discovery of the remains of animals in parts 
of the world where the nearest allied species could not now exist ; and 
it has also been supposed that the extinct faunas of Northern Europe 
indicate a climate nearly tropical. It is probable however that this 
law has been the result of a generalization somewhat too hasty, the 
most that we can at present safely assert being, that there have existed 
different climates at the same spot at different geological epochs, and 
that the changes in the cases we are best acquainted with were some- 
times, and most frequently, from a higher temperature to a lower, but 
sometimes also from a lower to a higher. 
«That the species belonging to the more ancient periods had a 
wider geographical distribution than the species now living, is a law 
rather indicated than demonstrated, and it is clear can only be definitely 
admitted when the numerous localities still unexamined have given 
evidence on the subject.’’ It was formerly considered by some geolo- 
gists, that “ the faunas of the most ancient formations are made up of 
the less perfectly organized animals, and the degree of perfection in- 
creases as we approach the more recent epochs.” 
In some of the early writers on cosmogony, the most absurd 
notions were entertained respecting bones of any extraordinary cha- 
racter ; they were considered to have belonged to fallen angels. After 
this, various conjectures on the nature of fossils appeared, and they 
