SIRENIA AND CETACEA. 



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the EliyncJioceti or Ziphioid Whales, and the Zeuglodontidm. 

 Of these, the Bcdmnidm are often spoken of as the " tooth- 

 less " Whales, whilst the other four families are called the 

 " toothed " Whales {Odontoceti). 



Fam. 1. BakmvidcB. — The Bcdmnidm or Toothless Whales 

 are characterised by the total absence of teeth in the adult 

 (fig. 620). Teeth, however, are present in the fostal Whale, 



Fig. 620.— Skull of the Right Whale (Balmna mysticetus). (After Owen.) 



but they never cut the gum. The place of teeth is supplied 

 by a number of plates of whalebone or " baleen " attached to 

 the palate ; hence the name of " Whalebone Whales " often 

 given to this family. They are the largest of living animals, 

 and may be divided into the two sections of the Smooth 

 Whales, in which the skin is smooth, and there is no dorsal 

 fin (as in the Greenland Whale), and the Furroiocd Whales, 

 in which the skin is furrowed, and a dorsal fin is present (as 

 in the so-called Tinner Whales and Hump-backed Whales). 



So far as at present known, the importance of the Bcdm- 

 nidm, from a pakeontological point of view, is not great. It 

 is very doubtful if any member of this group has been found 

 in any Secondary deposit. The only exception to this state- 

 ment — and it is a doubtful one — is that of the cervical verte- 

 brae of Pcdceocet'us, which were discovered in glacial accumu- 

 lations near Ely, and are supposed to have been washed out 

 of the Kimmeridge Clay (Jurassic). These are believed to 

 belong to a Whalebone Whale. In the Miocene and Pliocene 

 Tertiary we meet for the first time with undoubted remains 

 of Bcdmnidm. Of this nature are the extinct Ho-plocdus of 

 the Pliocene, and the Cetotherium and Cetotheriopsis of the 



