158 Darwin, and after Darwin. 
as we well know, the opportunities which the geo- 
logist has of discovering fossils are extremely limited, 
if we consider these opportunities in relation to the 
area of geological formations. The larger portion of 
the earth’s surface is buried beneath the sea; and 
much the larger portion of the fossiliferous deposits 
on shore are no less hopelessly buried beneath the 
land. Therefore it is only upon the fractional portion 
of the earth’s surface which at the present time 
happens to be actually exposed to his view that the 
geologist is able to prosecute his search for fossils. 
But even here how miserably inadequate this search 
has hitherto been! With the exception of a scratch 
or two in the continents of Asia and America, 
together with a somewhat larger number of similar 
scratches over the continent of Europe, even that 
comparatively small portion of the earth’s surface 
which is available for the purpose has been hitherto 
quite unexplored by the paleontologist. How enor- 
mously rich a store of material remains to be 
unearthed by the future scratchings of this surface, 
we may dimly surmise from the astonishing world of 
bygone life which is now being revealed in the newly 
discovered fossiliferous deposits on the continent of 
America. 
But, besides all this, we must remember, in the 
second place, that all the fossiliferous deposits in the 
world, even if they could be thoroughly explored, 
would still prove highly imperfect, considered as a 
history of extinct forms of life. In order that many 
of these forms should have been preserved as fossils, 
it is necessary that they should have died upon a 
surface neither too hard nor too soft to admit of their 
