LITTORAL DISTRICTS. 227 



northeastern limit is soon reached at Natal, the species which character- 

 ize the great Indo-Pacific Belt and the Indian District extending as far south 

 as that. 



Echinus subangulosus and Echinocardium australe, two of the characteristic 

 species of the district, extend to a great distance, in one case as far as the 

 Nikobar Islands, while Echinocardium australe is, with the exception of 

 the southern extremity of South America, found in the great Antarctic Belt, 

 extending from New Zealand to the Cape of Good Hope, and even passing 

 the equator and extending to Japan, in a similar manner to the extension 

 of Echinocardium cordatum from Norway to Bahia. Echinometra lucunter 

 extends on the eastern coast of Africa very far south, while Diadema seto- 

 sum, a cosmopolitan species, unites the West African and the Indo-Pacific 

 Districts. 



Another species is also found there, which is an antarctic type, Gonioci- 

 daris canaliculata ; this thus far is the only southern Circumpolar species 

 found, and, like E. australe, extends far north, being found at Zanzibar, 

 Sandwich Islands, and Navigator Islands, if the localities are to be trusted. 



Indo-Pacific District (PL A). 



In the great Indo-Pacific Belt the range of the species is very extensive. 

 It is characterized as a distinct belt, not only by its Echinoderms, but also 

 by its other Badiates, Mollusca, and Articulates. Better explored, as far as 

 its littoral fauna is concerned, than the corresponding parts of the Atlantic 

 Ocean, this belt extends on both sides of the equator in the Pacific, reaching 

 from the Sandwich Islands to the East Coast of Africa, comprising the Low 

 Archipelago, the Feejee and Navigator Islands, the north part of New Zea- 

 land, New Caledonia, New Guinea, the north shore of Australia, the whole 

 of the East Indian Archipelago, the Bay of Bengal, the Arabian Sea, the Bed 

 • Sea, and the East Coast of Africa as far as Natal, including the Seychelles, 

 Mascerene Islands, and Madagascar, and extending north as far as the Phi- 

 lippines, the Bonin Islands, and the southern extremity of Japan. This great 

 Indo-Pacific Belt encroaches upon the Australian District in New Zealand, 

 and the western and eastern coast of Australia, upon the Chinese and Jap- 

 anese District, and touches the west coast of Central America in the Pana- 

 mic District, while the Indo-African District, as well as the East Indian 

 and Pacific Districts, are both contained within the limits of this great belt. 

 The Indo-Pacific species having the most extensive range are : — 



