156 
ZOOLOGICAL GEOGRAPHY. 
[PAET III. 
America corresponds generally with that of the European Miocene, 
yet many of the tropical, and especially the Australian types, 
such as HaJcea and Dryandra, are absent. Owing to the recent 
discovery of a rich Cretaceous flora in North America, pro- 
bably of the same age as that of Aix-la-Chapelle in Europe, we 
are able to continue the comparison; and it appears, that at 
this early period the difference was still more marked. The 
predominant feature of the European Cretaceous flora seems to 
have been the abundance of Proteaceee, of which seven genera 
now living in Australia or the Cape of Good Hope have been 
recognised, besides others which are extinct. There are also 
several species of Pandanus, or screw-pine, now confined to the 
tropics of the Eastern Hemisphere, and along with these, oaks, 
pines, and other more temperate forms. The North American 
Cretaceous flora, although far richer than that of Europe, contains 
no Proteaceee or Pandani, but immense numbers of forest trees 
of living and extinct genera. Among the former we have oaks, 
beeches, willows, planes, alders, dog-wood, and cypress ; together 
with such American forms as magnolias, sassafras, and lirioden- 
drons. There are also a few not now found in America, as 
Araucaria and Cinnamomum, the latter still living in Japan. 
This remarkable flora has been found over a wide extent of 
country — New Jersey, Alabama, Kansas, and near the sources of 
the Missouri in the latitude of Quebec — so that we can hardly 
impute its peculiarly temperate character to the great elevation 
of so large an area. The intervening Eocene flora approximates 
closely, in North America, to that of the Miocene period ; while 
in Europe it seems to have been fully as tropical in character as 
that of the preceding Cretaceous period ; fruits of Nvpa, Pandanus, 
Anona, Acacia , and many Proteaceee, occurring in the London 
clay at the mouth of the Thames. 
These facts appear, at first sight, to be inconsistent, unless we 
suppose the climates of Europe and North America to have been 
widely different in these early times ; but they may perhaps be 
harmonised, on the supposition of a more uniform and a some- 
what milder climate then prevailing over the whole Northern 
Hemisphere ; the contrast in the vegetation of these countries 
