352 Mli. p. L. SCT;ATER ON THE [Mai*. 16, 



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 fcSteller, its discoverer, left to posterity a good 

 accoimt of its habits and anatomy. 



IV. Distrihutioii 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 consider the True or AVhalebone Whales, which 

 consist of a single family Balsenidae, usually divided into five 

 genera : — Balcvna, Neohaktnu, Rhachianectes, Megapteni, a.ndBalceiw- 

 j)tera. Of these, Balcena, Megaptera, and Bahvnoptem are almost 

 cosmopolitan — species of them, whether distinct or not is at 

 present more or less uncertain, being met witli in nearly every 

 pai't of the Ocean. But Rhachianectes has as yet been ascertained 

 to occur only in the Northern Pacific, and Ncobalcna 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 embrar/e at least four 

 existing families besides several extinct forms. The first family, 

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

 six genera (Physcter, C'ogla, Hyperoodon, Ziphius, Mesoplodon, and 

 Berardius). Fhyseter 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 part of the Ocean. Mesoplodon is also widely 

 distributed, but is apparently more abundant in the Southern 

 Hemisphere. Berardius, however, so far as we know at present, is 

 restricted to the South Polar Ocean. 



The third family of Toothed Whales contains only the Plata- 

 nistida', or Fi'eshwater Dolphins, which although, in some cases, 

 at the present day entirely fiuviatile, must probably have descended 

 from oceanic forms '. The three knov\'u genera are Flatanista of the 

 Ganges and Indus, Inia of the river Amazons, and Pontoporia of 

 the river La Plata ; the last form making a connecting hnk between 

 the two preceding genera and the marine Dolphins. 



The fourth family of Toothed AVhales, containing the Dolphins, 

 DeJphinida;, is very mimerous in species and embraces at least 

 fifteen or sixteen genera. But in spite of the efforts of Mr. True, 

 who has recently given us an excellent summary of our present 

 knowledge of them '^, both the genera and species of JJdphinidai 

 are still so imperfectly understood that I cannot say much about 



1 Sir William Flower (" Whales, Past and rreseut," rroc. Eoy. Inst. x. p. 360, 

 1883) rather favours the idea of a freshwater origin of the Cetaceans. 



2 See "AEeview of the Family- Delphiuida',' by Frederick W.True: Bull. 

 U.S. Nat. Mus. no. 3li (Washiugtou, U.S., 1889). 



