82 ZOOLOGICAL GEOGRAPHY. [part hi. 



Camivorn. Later, it received its Camelidoe, peccaries, mastodons, 

 and large Garni vora; and later still, just before the Glacial 

 epoch, its deer, tapir, opossums, antelopes, and horses, the two 

 latter having since become extinct. All this time its surface 

 was undergoing important physical changes. Wliat its earlier 

 condition was we cannot conjecture, but there are clear indica- 

 tions that it has been broken up into at least tliree large masses, 

 and probably a number of smaller ones ; and these have no 

 doubt undergone successive elevations and subsidences, so as 

 at one time to reduce their area and separate them still more 

 widely from each other, and at another period to unite them 

 into continental masses. The richness and varied development 

 of the old fauna of South America, as still existing, proves, liow- 

 ever, that the country has always maintained an extensive area ; 

 and there is reason to believe that the last great change has 

 been a long continued and steady increase of its surface, 

 resulting in the formation of the vast alluvial plains of the 

 Amazon, Orinoko, and La Plata, and tlnis greatly favouring 

 the production of that wealth of specific forms, which dis- 

 tinguishes South America above all other parts of our globe. 

 , The southern temperate portion of tlie continent, has probably 

 had a considerable southward extension in late Tertiary times ; 

 and this, as Avell as the comparatively recent elevation of tlie 

 Andes, has given rise to some degree of intermixture of two 

 distinct faunas, with tliat proper to South Temperate America 

 itself. The most important of these, is the considerable Austra- 

 lian element that appears in the insects, and even in the reptiles 

 and fresh-water fislies, of South Temperate America. These may 

 be traced to several causes. Icebergs and icefloes, and even 

 solid fields of ice, may, during the Glacial epoch, have afforded 

 many opportunities for the passage of the more cold-enduring 

 groups; wliile the greater extension of southern lands and 

 islands during the warm ])eriods — which there is reason to 

 believe prevailed in the southern as well as in the nortliern 

 regions in Miocene times— would afford facilities for tlie passage 

 of the reptiles and insects of more temperate zones. That )i(t 

 actual land-connection occurred, is prove:! by the total nbsonce 



