general parallelism in the successive
Silurian deposits of Bohemia and Scandinavia; nevertheless he finds a
surprising amount of difference in the species. If the several formations
in these regions have not been deposited during the same exact {329}
periods,--a formation in one region often corresponding with a blank
interval in the other,--and if in both regions the species have gone on
slowly changing during the accumulation of the several formations and
during the long intervals of time between them; in this case, the several
formations in the two regions could be arranged in the same order, in
accordance with the general succession of the form of life, and the order
would falsely appear to be strictly parallel; nevertheless the species
would not all be the same in the apparently corresponding stages in the two
regions.

_On the Affinities of extinct Species to each other, and to living
forms._--Let us now look to the mutual affinities of extinct and living
species. They all fall into one grand natural system; and this fact is at
once explained on the principle of descent. The more ancient any form is,
the more, as a general rule, it differs from living forms. But, as Buckland
long ago remarked, all fossils can be classed either in still existing
groups, or between them. That the extinct forms of life help to fill up the
wide intervals between existing genera, families, and orders, cannot be
disputed. For if we confine our attention either to the living or to the
extinct alone, the series is far less perfect than if we combine both into
one general system. With respect to the Vertebrata, whole pages could be
filled with striking illustrations from our great palaeontologist, Owen,
showing how extinct animals fall in between existing groups. Cuvier ranked
the Ruminants and Pachyderms, as the two most distinct orders of mammals;
but Owen has discovered so many fossil links, that he has had to alter the
whole classification of these two orders; and has placed certain pachyderms
in the same sub-order with ruminants: for example, he dissolves by fine
gradations the apparently {330} wide difference between the pig and the
camel. In regard to the Invertebrata, Barrande, and a higher authority
could not be named, asserts that he is every day taught that Palaeozoic
animals, though belonging to the same orders, families, or genera with
those living at the present day, were not at this early epoch limited in
such distinct gr