392 
ISLAND LIFE. 
[part II. 
important a part of the fauna of Madagascar as well as of 
Africa, were abundant in Europe throughout the whole Ter- 
tiary period, but are not known to have ever lived in any part 
of the American continent. We here see the application of 
the principle which we have already fully proved and illustrated 
(Chapter IV., p. 62), that all extensive groups have a wide range 
at the period of their maximum development ; but as they 
decay their area of distribution diminishes or breaks up into 
detached fragments, which one after another disappear till the 
group becomes extinct. Those animal forms which we now 
find isolated in Madagascar and other remote portions of the 
globe all belong to ancient groups which are in a decaying or 
nearly extinct condition, while those which are absent from it 
belong to more recent and more highly-developed types, which 
range over extensive and continuous areas, but have had no 
opportunity of reaching the more ancient continental islands. 
Anomalies of Distribution and how to explain them . — If these 
considerations have any weight, it follows that there is no reason 
whatever for supposing any former direct connection between 
Madagascar and the Greater Antilles merely because the In- 
sectivorous Oentetidse now exist only in these two groups of 
islands ; for we know that the ancestors of this family must 
once have had a much wider range, which almost certainly 
extended over the great northern continents. We might as 
reasonably suppose a land-connection across the Pacific to ac- 
count for the ‘ camels of Asia having their nearest existing 
allies in the llamas and alpacas of the Peruvian Andes, and 
another between Sumatra and Brazil, in order that the ances- 
tral tapir of one country might have passed over to the other. 
In both these cases we have ample proof of the former wide 
extension of the group. Extinct camels of numerous species 
abounded in North America in Miocene, Pliocene, and even 
Post-pliocene times, and one has also been found in North- 
western India, but none whatever among all the rich deposits 
of mammalia in Europe. We are thus told, as clearly as pos- 
sible, that from the North American continent as a centre the 
camel tribe spread westward, over now-submerged land at the 
shallow Behring Straits and Kamschatka Sea, into Asia, and 
