→ in any one region for the immigration of 1860 1861 1866 1869 1872 |
for the coming in of quite 1859 |
|
→ from other regions, 1860 1861 1866 1869 1872 |
by immigration, 1859 |
|
→ mastodons 1859 1860 1861 1866 1869 |
the species of mastodons 1872 |
|
→ series, first 1859 1860 1861 1866 1869 |
series,— in the first place 1872 |
|
→ then 1859 1860 1861 1866 1869 |
in the second place 1872 |
|
→ perfect, 1859 1860 1861 1866 1869 |
complete, which is far from the case, 1872 |
|
character between the forms of life above and below. We must, however, allow for the entire extinction of some preceding forms, and
→in any one region for the immigration of
new forms
→from other regions,
and for a large amount of
during the long and blank intervals between the successive formations. Subject to these allowances, the fauna of each geological period undoubtedly is intermediate in character, between the preceding and succeeding faunas. I need give only one instance, namely, the manner in which the fossils of the Devonian system, when this system was first discovered, were at once recognised by palæontologists as intermediate in character between those of the overlying carboniferous, and underlying Silurian
But each fauna is not necessarily exactly intermediate, as unequal intervals of time have elapsed between consecutive formations. |
|
It is no real objection to the truth of the
that the fauna of each period as a whole is nearly intermediate in character between the preceding and succeeding faunas, that certain genera offer exceptions to the rule. For instance,
→mastodons
and elephants, when arranged by Dr. Falconer in two
→series, first
according to their mutual
and
→then
according to their periods of
do not accord in arrangement. The species extreme in character are not the
or the most recent; nor are those which are intermediate in character, intermediate in age. But supposing for an instant, in this and other such cases, that the record of the first appearance and disappearance of the species was
→perfect,
we have no reason to believe that forms successively produced necessarily endure for corresponding lengths of
very ancient form
occasionally
much longer than a form
subsequently produced, especially in the case of
|