iQ14 Prof. J. Van der Hoeven on the Succession and 
there can be no reason given why their remains, their bones &c., 
were never found together with the remains of the extinct spe- 
cies alluded to. Perhaps the first thesis seems not so clear— 
that those species which we find in the strata of different aqueous 
rocks and deposits are truly extinct. Some may be disposed to 
ask whether our survey of the now living organic world is so 
complete that we know all the species. This is certainly not the 
case ; but the chances of discovering species similar to those we 
know as yet only as fossils decrease daily, and the whole objec- 
tion loses its strength because geological investigations teach us 
that the animals and plants of older strata are specifically dif- 
ferent from those of recent ones. Thus not only one series of 
organisms is extinct, but there are several such series, the one 
succeeding the other. Species of the different tertiary strata 
are different from each other. All these are different from those 
of the Chalk formation ; those of the Chalk formation are unlike 
those of the Oolitic SEG, ; others, again, are to be found in the 
strata of the New Red Sandstone, others in the Coal formation 
&e., all differing. 
That some species became extinct seems in general a fact that 
is not so strange as that some species originated in succession— 
that there were consecutive and distinct creations of organic 
forms. Of the first fact we do not want examples, even in 
recent periods, within the three last centuries of history. I 
may refer to the well-ascertained fact of the extinction of the 
Dodo—a bird recorded to have been seen by several travellers, 
and represented in various pictures and prints. Greater still is _ 
the number of instances of local exterminations, local extinctions 
of species. In many civilized parts of Europe several species 
have now totally disappeared, which formerly were not uncom- 
mon in the same localities. At the time of Xerxes lions lived 
in Greece, and attacked the camels of his army*. Even a cen- 
tury and a half after that time, lions are mentioned by Aristotle 
as living in Europet. In many parts of Europe the beaver was 
common in the middle ages, where it is now entirely unknown. 
In Wales and Scotland the bear was found in the first ten cen- 
turies of the Christian eva; and even the wolf was not entirely 
extirpated till about the end of the 17th century{. The extine- 
tion of species in preehistorical times, in the different geological 
periods which elapsed before the appearance of man, differs only 
in being more general—we should almost say, in being total, if 
the investigations of Ehrenberg did not teach us that some 
* Herodot. vii. 125, 126. + Hist. Animal. viii. 
t In 1680, when the last wolf fell by the hand of the famous Sir Ewen 
Cameron. (Thos. Pennant’s ‘British Zoology,’ new ed., London, 1812, 
p- 88.) 
