378 
DARWINISM 
CHAP. 
found in a space 300 paces long by 60 paces broad, many of 
the species existing in enormous quantities. 
The Pikermi fossils belong to the Upper Miocene forma¬ 
tion, but an equally rich deposit of Upper Eocene age has 
been discovered in South-Western France at Quercy, where M. 
Filhol has determined the presence of no less than forty-two 
species of beasts of prey alone. Equally remarkable are the 
various discoveries of mammalian fossils in North America, 
especially in the old lake bottoms now forming what are 
called the “bad lands” of Dakota and Nebraska, belonging to 
the Miocene period. Here are found an enormous assemblage 
of remains, often perfect skeletons, of herbivora and carnivora, 
as varied and interesting as those from the localities already 
referred to in Europe; but altogether distinct, and far ex¬ 
ceeding, in number and variety of species of the larger animals, 
the whole existing fauna of North America. Very similar 
phenomena occur in South America and in Australia, leading 
us to the conclusion that the earth at the present time is 
impoverished as regards the larger animals, and that at each 
successive period of Tertiary time, at all events, it contained 
a far greater number of species than now inhabit it. The 
very richness and abundance of the remains which we find 
in limited areas, serve to convince us how imperfect and 
fragmentary must be our knowledge of the earth’s fauna at 
any one past epoch ; since we cannot believe that all, or 
nearly all, of the animals which inhabited any district were 
entombed in a single lake, or overwhelmed by the Hoods of a 
single river. 
But the spots where such rich deposits occur are ex¬ 
ceedingly few and far between when compared with the vast 
areas of continental land, and we have every reason to believe 
that in past ages, as now, numbers of curious species were 
rare or local, the commoner and more abundant species giving 
a very imperfect idea of the existing series of animal forms. 
Vet more important, as showing the imperfection of our 
knowledge, is the enormous lapse of time between the several 
formations in which we find organic remains in any abundance, 
so vast that in many cases we find ourselves almost in a new 
world, all the species and most of the genera of the higher 
animals having undergone a complete change. 
