The supposition that all these types were
rapidly differentiated out of _Lacertilia_, in the time represented by
the passage from the Palaeozoic to the Mesozoic formation, appears to
me to be hardly more credible, to say nothing of the indications of
the existence of Dinosaurian forms in the Permian rocks which have
already been obtained.
For my part, I entertain no sort of doubt that the Reptiles, Birds,
and Mammals of the Trias are the direct descendants of Reptiles,
Birds, and Mammals which existed in the latter part of the Palaeozoic
epoch, but not in any area of the present dry land which has yet been
explored by the geologist.
This may seem a bold assumption, but it will not appear unwarrantable
to those who reflect upon the very small extent of the earth's surface
which has hitherto exhibited the remains of the great Mammalian fauna
of the Eocene times. In this respect, the Permian land Vertebrate
fauna appears to me to be related to the Triassic much as the Eocene
is to the Miocene. Terrestrial reptiles have been found in Permian
rocks only in three localities; in some spots of France, and recently
of England, and over a more extensive area in Germany. Who can suppose
that the few fossils yet found in these regions give any sufficient
representation of the Permian fauna?
It may be said that the Carboniferous formations demonstrate the
existence of a vast extent of dry land in the present dry-land area,
and that the supposed terrestrial Palaeozoic Vertebrate Fauna ought to
have left its remains in the Coal-measures, especially as there is now
reason to believe that much of the coal was formed by the accumulation
of spores and sporangia on dry land.
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