Turning to
the Invertebrata, Barrande asserts, a higher authority could not be named,
that he is every day taught that, although palaeozoic animals can certainly
be classed under existing groups, yet that at this ancient period the
groups were not so distinctly separated from each other as they now are.
Some writers have objected to any extinct species, or group of species,
being considered as intermediate between any two living species, or groups
of species. If by this term it is meant that an extinct form is directly
intermediate in all its characters between two living forms or groups, the
objection is probably valid. But in a natural classification many fossil
species certainly stand between living species, and some extinct genera
between living genera, even between genera belonging to distinct families.
The most common case, especially with respect to very distinct groups, such
as fish and reptiles, seems to be that, supposing them to be distinguished
at the present day by a score of characters, the ancient members are
separated by a somewhat lesser number of characters, so that the two groups
formerly made a somewhat nearer approach to each other than they now do.
It is a common belief that the more ancient a form is, by so much the more
it tends to connect by some of its characters groups now widely separated
from each other. This remark no doubt must be restricted to those groups
which have undergone much change in the course of geological ages; and it
would be difficult to prove the truth of the proposition, for every now and
then even a living animal, as the Lepidosiren, is discovered having
affinities directed towards very distinct groups.
Pages:
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569