THE DISTRIBUTION OF ANIMALS 445 



South America, with newer mammals, has older reptiles; 

 while Africa has a rich vertebrate life, with a striking 

 uniformity in its distribution. Groups, old geologically 

 and now nearly extinct, are apt to have a peculiar dis- 

 tribution ; as the Edentata in South America, Africa, 

 and India ; the marsupials in Australia and America ; 

 the Ratitae in South America, Africa, Australia, and 

 New Zealand. 



In the tropics, diversity is the law. Life is more 

 varied and crowded than elsewhere, and attains its 

 highest development. 



The New World fauna is old-fashioned, and inferior 

 in rank and size, compared with that of the eastern 

 continents. 



As a rule, the more isolated a region the greater the 

 variety. Oceanic islands have comparatively few species, 

 but a large proportion of endemic or peculiar forms. 

 Batrachians are absent, and there are no indigenous 

 terrestrial mammals. The productions are related to 

 those of the nearest continent. When an island, as 

 Britain, is separated from the mainland by a shallow 

 channel, the mammalian life is the same on both sides. 



Protozoans, ccelenterates, and echinoderms are limited 

 to the waters, and nearly all are marine. Sponges are 

 mostly obtained from the Grecian Archipelago and 

 Bahamas, but species not commercially valuable abound 

 in all seas. Coral reefs abound throughout the Indian 

 Ocean and Polynesia, east coast of Africa, Red Sea, 

 and Persian Gulf, West Indies, and around Florida; 

 and corals which do not form reefs are much more 

 widely distributed, being found as far north as Long 

 Island Sound and England. Crinoids have been found, 

 usually in deep sea, in very widely separated parts of 

 the world off the coast of Norway, Scotland, and 

 Portugal, and near the East and West Indies. The 



