re really birds. Until
quite recently these authors might have maintained, and some have
maintained, that the whole class of birds came suddenly into existence
during an early tertiary period; but now we know, on the authority of
Professor Owen (as may be seen in Lyell's 'Manual'), that a bird certainly
lived during the deposition of the upper greensand.

I may give another instance, which from having passed under my own eyes has
much struck me. In a memoir on Fossil Sessile Cirripedes, I have stated
that, from the {305} number of existing and extinct tertiary species; from
the extraordinary abundance of the individuals of many species all over the
world, from the Arctic regions to the equator, inhabiting various zones of
depths from the upper tidal limits to 50 fathoms; from the perfect manner
in which specimens are preserved in the oldest tertiary beds; from the ease
with which even a fragment of a valve can be recognised; from all these
circumstances, I inferred that had sessile cirripedes existed during the
secondary 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. 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 palaeontologists 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 palaeontologists believe that
certain {306} much older fishes, of which the affinities are as yet
imper