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known nothing whatsoever of the existence of the reptile whose bones it
had encased。
How certain it is that a vast number of animals which have existed at
one period on this earth have entirely perished； and left no trace
whatever of their forms； may be proved to you by other considerations。
There are large tracts of sandstone in various parts of the world； in
which nobody has yet found anything but footsteps。 Not a bone of any
description； but an enormous number of traces of footsteps。 There is
no question about them。 There is a whole valley in Connecticut covered
with these footsteps； and not a single fragment of the animals which
made them has yet been found。 Let me mention another case while upon
that matter； which is even more surprising than those to which I have
yet referred。 There is a limestone formation near Oxford； at a place
called Stonesfield； which has yielded the remains of certain very
interesting mammalian animals； and up to this time； if I recollect
rightly； there have been found seven specimens of its lower jaws； and
not a bit of anything else； neither limb…bones nor skull； or any part
whatever； not a fragment of the whole system！ Of course； it would be
preposterous to imagine that the beasts had nothing else but a lower
jaw！ The probability is； as Dr。 Buckland showed； as the result of his
observations on dead dogs in the river Thames； that the lower jaw； not
being secured by very firm ligaments to the bones of the head； and
being a weighty affair； would easily be knocked off； or might drop away
from the body as it floated in water in a state of decomposition。 The
jaw would thus be deposited immediately； while the rest of the body
would float and drift away altogether； ultimately reaching the sea； and
perhaps becoming destroyed。 The jaw becomes covered up and preserved in
the river silt； and thus it comes that we have such a curious
circumstance as that of the lower jaws in the Stonesfield slates。 So
that； you see； faulty as these layers of stone in the earth's crust
are； defective as they necessarily are as a record； the account of
contemporaneous vital phenomena presented by them is； by the necessity
of the case； infinitely more defective and fragmentary。
It was necessary that I should put all this very strongly before you；
because； otherwise； you might have been led to think differently of the
completeness of our knowledge by the next facts I shall state to you。
The researches of the last three…quarters of a century have； in truth；
revealed a wonderful richness of organic life in those rocks。 Certainly
not fewer than thirty or forty thousand different species of fossils
have been discovered。 You have no more ground for doubting that these
creatures really lived and died at or near the places in which we find
them than you have for like scepticism about a shell on the sea…shore。
The evidence is as good in the one case as in the other。
Our next business is to look at the general character of these fossil
remains； and it is a subject which it will be requisite to consider
carefully； and the first point for us is to examine how much the
extinct 'Flora' and 'Fauna' as a 'whole'disregarding altogether the
'succession' of their constituents； of which I shall speak
afterwardsdiffer from the 'Flora' and 'Fauna' of the present
day；how far they differ in what we 'do' know about them； leaving
altogether out of consideration speculations based upon what we 'do
not' know。
I strongly imagine that if it were not for the peculiar appearance that
fossilised animals have； any of you might readily walk through a museum
which contains fossil remains mixed up with those of the present forms
of life； and I doubt very much whether your uninstructed eyes would
lead you to see any vast or wonderful difference between the two。 If
you looked closely； you would notice； in the first place； a great many
things very like animals with which you are acquainted now： you would
see differences of shape and proportion； but on the whole a close
similarity。
I explained what I meant by ORDERS the other day； when I described the
animal kingdom as being divided in sub…kingdoms； classes and orders。 If
you divide the animal kingdom into orders； you will find that there are
about one hundred and twenty。 The number may vary on one side or the
other； but this is a fair estimate。 That is the sum total of the orders
of all the animals which we know now； and which have been known in past
times； and left remains behind。
Now； how many of those are absolutely extinct？ That is to say； how many
of these orders of animals have lived at a former period of the world's
history； but have at present no representatives？ That is the sense in
which I meant to use the word 〃extinct。〃 I mean that those animals did
live on this earth at one time； but have left no one of their kind with
us at the present moment。 So that estimating the number of extinct
animals is a sort of way of comparing the past creation as a whole with
the present as a whole。 Among the mammalia and birds there are none
extinct； but when we come to the reptiles there is a most wonderful
thing： out of the eight orders； or thereabouts； which you can make among
reptiles； one…half are extinct。 These diagrams of the plesiosaurus；
the ichthyosaurus； the pterodactyle； give you a notion of some of these
extinct reptiles。 And here is a cast of the pterodactyle and bones of
the ichthyosaurus and the plesiosaurus； just as fresh as if it had been
recently dug up in a churchyard。 Thus； in the reptile class； there are
no less than half of the orders which are absolutely extinct。 If we
turn to the 'Amphibia'； there was one extinct order； the
Labyrinthodonts； typified by the large salamander…like beast shown in
this diagram。
No order of fishes is known to be extinct。 Every fish that we find in
the stratato which I have been referringcan be identified and
placed in one of the orders which exist at the present day。 There is
not known to be a single ordinal form of insect extinct。 There are
only two orders extinct among the 'Crustacea'。 There is not known to
be an extinct order of these creatures； the parasitic and other worms；
but there are two； not to say three； absolutely extinct orders of this
class； the 'Echinodermata'； out of all the orders of the 'Coelenterata'
and 'Protozoa' only one； the Rugose Corals。
So that； you see； out of somewhere about 120 orders of animals； taking
them altogether； you will not； at the outside estimate； find above ten
or a dozen extinct。 Summing up all the orders of animals which have
left remains behind them； you will not find above ten or a dozen which
cannot be arranged with those of the present day； that is to say； that
the difference does not amount to much more than ten per cent。： and the
proportion of extinct orders of plants is still smaller。 I think that
that is a very astounding； a most astonishing fact； seeing the enormous
epochs of time which have elapsed during the constitution of the surface
of the earth as it at present exists； it is； indeed； a most astounding
thing that the proportion of extinct ordinal types should be so
exceedi