CHAPTER XXX 

 CETACEANS continued 



THE TOOTHED WHALES, OR ODONTOCEIES 



THE whole of the remainder of the existing Cetaceans form a group dis- 

 tinguished from the preceding one by the absence of whalebone, and the presence of 

 permanent teeth in at least the lower jaw. This group, comprising existing 

 families, is known as the Odontoceti, or Toothed Cetaceans, in contradistinction to 

 the Mystacoceti, or Whalebone Whales. 



In addition to the presence of teeth, the group is also characterized by the fol- 

 lowing distinctive features. The two nostrils unite before they reach the surface, 

 and thus open by a single aperture, which usually takes the form of a crescentic 

 valvular slit placed transversely to the long axis of the head. In the skull, the 

 bones of the upper surface are arranged unsymmetrically on the sides; the nasal 

 bones in existing forms being reduced to nodules, taking no share in roofing over 

 the cavity of the nostrils. The two branches of the lower jaw are nearly straight, 

 and of great vertical extent behind, while in front they come in contact with one 

 another by flattened surfaces of larger or smaller extent, as is ordinarily the case 

 among Mammals. The ribs are more firmly joined to the rest of the skeleton than 

 in the whalebone whales, several of the anterior pairs articulating w r ith the bodies 

 as well as with the horizontal transverse processes of the vertebrae, while below they 

 are joined to the breast bone by the intervention of so-called chest ribs: the breast- 

 bone itself usually consisting of several distinct portions, placed one behind the 

 other. In all cases the flippers have five digits. 



SPERM WHALES AND THEIR ALLIES 

 Family PHTSE TERID^E 



The well-known gigantic sperm whale is the typical representative of a family 

 characterized by the total absence of any functional teeth in the upper jaw; those 

 of the lower jaw being either numerous or reduced to a single pair. These charac- 

 teristics are sufficient to distinguish the members of this family from those of the 

 two others now existing, but it may be added that the skull is elevated in the hinder 

 region, so as to form a high prominence or crest behind the aperture of the nostrils. 



The members of this family include the largest of the toothed Cetaceans, and 

 the whole of them are exclusively oceanic in their habits; their food consisting 

 mainly or solely of squids and cuttles. 



("95) 



