sessile cirripede, which he had himself extracted from the chalk of
Belgium. And, as if to make the case as striking as possible, this
sessile cirripede was a Chthamalus, a very common, large, and
ubiquitous genus, of which not one specimen has as yet been found even
in any tertiary
stratum. Hence we now positively know that sessile cirripedes existed
during the secondary period; and these cirripedes might have been the
progenitors of our many tertiary and existing species.
The case most frequently insisted on by pal ontologists of the
apparently sudden appearance of a whole group of species, is that of
the teleostean fishes, low down in the Chalk period. This group
includes the large majority of existing species. Lately, Professor
Pictet has carried their existence one sub-stage further back; and some
pal ontologists believe that certain much older fishes, of which the
affinities are as yet imperfectly known, are really teleostean.
Assuming, however, that the whole of them did appear, as Agassiz
believes, at the commencement of the chalk formation, the fact would
certainly be highly remarkable; but I cannot see that it would be an
insuperable difficulty on my theory, unless it could likewise be shown
that the species of this group appeared suddenly and simultaneously
throughout the world at this same period. It is almost superfluous to
remark that hardly any fossil-fish are known from south of the equator;
and by running through Pictet s Pal ontology it will be seen that very
few species are known from several formations in Europe. Some few
families of fish now have a confined range; the teleostean fish might
formerly have had a similarly confined range, and after having been
largely developed in some one sea, might have spread widely. Nor have
we any right to suppose that the seas of the world have always been so
freely open from south to north as they are at present. Even at this
day, if the Malay Archipelago were converted into land, the tropical
parts of the Indian Ocean would form a large and perfectly enclosed
basin, in which any great group of marine animals might be multiplied;
and
here they would remain confined, until some of the species became
adapted to a cooler climate, and were enabled to double the southern
capes of Africa or Australia, and thus reach other and distant seas.
From these and similar considerations, but chiefly from our ignorance
of the geology of other countries beyond the confines of Europe and the
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