Distribution of Marine Mammalia. 267 



essentially an Antarctic form, though now nearly extinct there, after 

 long persecution by man. But, as already noted, it extends, or has 

 in former days extended, far up the West coast of America, and 

 is still occasionally found on Santa Barbara Island on the coast of 

 California. 



III. Distribution of Sirenians. — Only two forms of Sirenians are 

 at the present time existing on the earth's surface — the Manatee 

 (Manatus) and Dugong {Halicore) — each representing a distinct 

 family of the order. The Manatee is an inhabitant of the coasts 

 and estuaries of both sides of the middle Atlantic Ocean — one 

 species (Manatus Senegalensis) occurring on the African shores, and 

 another (ilf. Aniericanus) on the South American coast and in the 

 Antilles. A third species (AT. inunguis), so far as we know at 

 present, is found only in fresh water high up the Amazons. 



The Dugong (Haiicore) is distributed from East Africa, along 

 the shores of the Indian Ocean and its islands, to North Australia. 

 Three species of this genus have been established — Halicore 

 tabernaculi from the Eed Sea, H. dugong from the Indian Ocean, 

 and H. Australis from Australia ; but it is doubtful how far these 

 forms are actually distinguishable. 



Beside Manatus and Halicore, a third quite distinct form of 

 Sirenian was formerly an inhabitant of the North Pacific. This 

 was Steller's Sea-cow (Bhytina Stelleri), by far the largest animal of 

 the group, which was exterminated by human agency about 1768. 

 Fortunately recent researches in Behring's Island have been suc- 

 cessful in supplying specimens of its skeleton for our principal 

 Museums, and Steller, its discoverer, left to posterity a good account 

 of its habits and anatomy. 



IV. Distribution of Cetaceans. — Adopting the recognized division 

 of the Cetaceans into two suborders, Mystacoceti and Odontoceti, 

 according as to whether their mouths are furnished with baleen 

 (" whalebone ") or teeth, we will jfirst consider the True or Whale- 

 bone Whales, which consist of a single family, Balsenidas, usually 

 divided into five genera : Balcsna, Neohalaina, Bhachianecles, 

 Megaptera, and Balcenoptera. Of these, Balcena, Meguptera, and 

 Balmioptera are almost cosmopolitan — species of them, whether 

 distinct or not is at present more or less uncertain, being met with 

 in nearly every part of the ocean. But Rhachianectes has as yet 

 been ascertained to occur only in the Northern Pacific, and 

 Neobalcena in the South Polar Ocean, so that we have in these 

 cases two well-marked local types to deal with. 



The Toothed Wales (Odontoceti) are more diversified than the 

 preceding group, and are usually held to embrace at least four 

 existing families besides several extinct forms. The first family, 

 containing the Physeteridee or Sperm- Whales, consists of at least 

 six genera (Physeter, Cogia, Hyperoodon, Zipliius, Mesoplodon, and 

 JJerardius). Pliyseter and Cogia are inhabitants of the whole oceanic 

 area between the tropics, extending in certain localities some way 

 beyond them, Hyperoodon is confined to the North Atlantic. 

 Ziphius has an extensive range, and has been found in nearly every 



