392 



ISLAND LIFE. 



[r'Airr 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 area&, but have had no 

 opportunity of reaching the more ancient continental islands. 



Anomalies of Distribution and hoiu to explain thein. — 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 Centetidse 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 



