May 14, 1897.] 



SCIENCE. 



743 



four species belonging to as many genera : 

 Ogmorhinus, Lobodon, Leptonychotes and Om- 

 matophoca. Besides these the sea-elephant 

 of the whalers (3Iacrorhimis) is essentially 

 an Antarctic form, though now nearly ex- 

 tinct 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 SIEENIANS. 



Only two forms of Sirenians are at the 

 present time existing on the earth's surface 

 — the Manatee (ilanatus) 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 {M. 

 americanus) on the South American coast 

 and in the Antilles. A third species (M. 

 inunguis) , so far as we know at present, is 

 found only in fresh water high up the 

 Amazons. 



The Dugong {Halicore) 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 In- 

 dian Ocean, and H. australis from Australia; 

 but it is doubtful how far these forms are 

 actually distinguishable. 



Besides Manatus and Halicore, a third 

 quite distinct form of Sirenian was formerly 

 an inhabitant of the North Pacific. This 

 was Steller's Sea-cow {Rhytina stelleri) , hy 

 far the largest animal of the group, which 

 was exterminated by human agency about 

 1768. Fortunately recent researches in 

 Bering's Island have been successful in 

 supplying specimens of its skeleton for our 

 principal museums, and Steller, its dis- 



coverer, 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 

 (' whale-bone ') or teeth, we will first con- 

 sider the True or Whale-bone Whales, 

 which consist of a single family, Balsenidse, 

 usually divided into five genera : JBalwna, 

 Neobalcena, Rhachianedes, Megaptera and Balce- 

 noptera. Of these, Balcena, Megaptera and 

 Bakenoptera are almost cosmopolitan — spe- 

 cies of them, whether distinct or not is at 

 present more or less uncertain, being met 

 with in nearly every part of the ocean. 

 But Rhachianedes has, as yet, been ascer- 

 tained to occur onljr in the Northern Pa- 

 cific, 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 

 Physeteridse, or Sperm-Whales, consists of 

 at least six genera (Physeter, Cogia, Hyper- 

 oodon, Ziphius, Mesoplodon and Berardius). 

 Physeter and Cogia are inhabitants of the 

 whole oceanic area between the tropics, ex- 

 tending in certain localities some way be- 

 yond them. Hyperoodon is confined to the 

 North Atlantic. Ziphius has an extensive 

 range, and has been found in nearly every 

 part of the ocean. Mesoplodon is also widely 

 distributed, but is apparently more abun- 

 dant in the Southern Hemisphere. Berar- 

 dius, however, so far as we know at present, 

 is restricted to the South Polar Ocean. 



The Third family of Toothed Whales con- 

 tains only the Platanistidae, or fresh-water 

 Dolphins, which although, in some cases at 

 the present day entirely fluviatile, must 



