282 Antediluvian Soology and Botany. 
may still be traced at intervals, and sparingly, in subjacent beds. 
In the beds succeeding the chalk, we have a remarkable excep- 
tion. At no point is there a more strongly marked change than 
is exhibited at the termination of this formation. The clays 
which follow are peopled by a multitude of animals differing 
essentially from all that had preceded them: an entirely new 
series, * not formed,” as Mr. Parkinson observes, “ by the 
gliding of one genus into another, or by changes induced in 
the structure of the animals, but, as far as the state of our 
knowledge will allow us to judge, by a new creation, adapted 
to the especial purposes which Providence had destined to 
accomplish.” 
One of the most remarkable facts elicited is, that certain Tes- 
tacea, whose genera were abundantly preserved and prolonged 
through so many formations, should now exist so sparingly, or 
be entirely lost. We might instance the Terebratulae, which 
abound no less in the mountain limestone than in the chalk, and 
in almost every intermediate rock, which are absent in nearly 
every one of our tertiary beds, ia reappear in the most recent. 
Not less than 100 fossil species of ‘Terebratulze, and myriads 
of individuals, are known to us; but the recent shells of this 
genus are comparatively few. Of Trigdnia, also, 25 species 
are found in our strata, often abundantly, and terminating, 
like the Ammonites, with the chalk. Until lately, this genus 
was considered to be extinct; but one species has been dis- 
covered on the shores of New Holland. Of Ammonites, so 
profusely distributed, whose species amount, it is said, to no 
less than 200, and of which about 175 are known in the 
English formations, none now remain. 29 species of Pro- 
dicta, 3 of Pentamerus, and 19 of Spirifer, inhabited the 
waters that produced the transition and mountain limestone, 
and contiguous shales; but these genera are altogether ex- 
tinct. Indeed, almost the whole series of antediluvian multi- 
locular shells seem to have shared a similar fate. 
On the other hand, instances are no less abundant and 
striking, where the recent species comprehended under certain 
genera do greatly outnumber the fossils. Thus, under the 
Linnean genus Conus are comprised 155 species existing ; but 
only 3 occur fossil in our London clay. The genus Cypre* a 
contains about 110 living species, and only 4 fossil in the ter- 
tiary beds. 
Thus, during the revolutions of ages, some races have 
been extinguished, and have given place to others which may 
still be traced in our seas. In the great tertiary deposits of 
the Sub-Apennines, Brocchi conceived he could point out some 
marine shells, which are now very widely dispersed, in the 
