376 COMPARATIVE ZOOLOGY. 



The New-world fauna is old-fashioned, and inferior in 

 ,rank and size, compared with that of the eastern con- 

 tinents. 



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. Ba- 

 trachians 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 sepa- 

 rated from the mainland by a ehallow channel, the mam- 

 malian 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 Baha- 

 mas, 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, be- 

 ing found as far north as Long Island Sound and Eng- 

 land. 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 other Echinoderms abound in almost 

 every sea : the Star-fishes chiefly along the shore, the Sea- 

 urchins in the Laminarian zone, and the Sea-slugs around 

 coral-reefs. Worms are found in all parts of the world, 

 in sea, fresh water, and earth. They are most plentiful 

 in the muddy or sandy bottoms of shallow seas. Living 

 Brachiopods, though few in number, occur in tropical, 

 temperate, and arctic seas, and from the shore to great 

 depths. Polyzoa have both salt and fresh water forms, 

 and Annelids include land forms, as the Earth-worm and 

 some Leeches. 



Mollusks have a world-wide distribution over land and 



