periods, they would certainly have been
preserved and discovered; and as not one species had then been
discovered in beds of this age, I concluded that this great group
had been suddenly developed at the commencement of the tertiary
series. This was a sore trouble to me, adding as I thought one more
instance of the abrupt appearance of a great group of species. But
my work had hardly been published, when a skilful palaeontologist,
M. Bosquet, sent me a drawing of a perfect specimen of an
unmistakeable 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. Still more
recently, a Pyrgoma, a member of a distinct sub-family of sessile
cirripedes, has been discovered by Mr. Woodward in the upper chalk;
so that we now have abundant evidence of the existence of this
group of animals during the secondary period.

The case most frequently insisted on by palaeontologists of the
apparently sudden appearance of a whole group of species, is that
of the teleostean fishes, low down, according to Agassiz, in the
Chalk period. This group includes the large majority of existing
species. But certain Jurassic and Triassic forms are now commonly
admitted to be teleostean; and even some palaeozoic forms have been
thus classed by one high authority. If the teleosteans had really
appeared suddenly in the northern hemisphere, the fact would have
been highly remarkable; but it would not have formed an insuperable
difficulty, unless it could likewise have been shown that at the
same period the species were suddenly and simultaneously developed
in other quarters of the world. It is almost superfluous to remark
that hardly any fossil fish are known from south of the equator;
and by running through Pictet's Palaeontology 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 t