SPERM WHALES AND BOTTLE-NOSED WHALES 269 



commercial importance of any kind. No information is 

 available about its swimming habits, and it is not known 

 whether or not it migrates. 



BOTTLE-NOSED OR BEAKED WHALES. 

 Family Ziphiid^e. 



The group of Bottle-nosed or Beaked Whales is made up of 

 a number of species of moderate-sized Cetaceans ranging from 

 about 15 to 30 feet in length. They resemble the Sperm Whale 

 in having functional teeth restricted to the lower jaws ; also 

 the skull bears a general similarity to that of the Sperm, for, 

 as in the latter creature, the bones behind the breathing orifices 

 are raised into a conspicuous crest, and the rostrum or forward 

 extension of the skull is elongated and tapering. Unlike the 

 Sperm Whale, however, which has a blunt and very massive 

 head, the Ziphioid Whales are characterized by a long narrowed 

 snout, which in some species is sharply defined from the rest 

 of the head and in others merges gradually into it. 



On the under surface of the throat are two deep longitu- 

 dinally running grooves in the skin, which almost meet in front 

 and diverge as they pass backward. The flippers are small in 

 all members of the group, and the dorsal fin, always situated 

 well behind the middle of the back, is triangular with concave 

 posterior border. The middle of the hinder border of the 

 flukes instead of being notched is slightly convex. 



At least one pair of teeth of moderate size is to be found in 

 the lower jaws, but in young specimens of both sexes and in 

 females irrespective of age these are embedded in the tissues 

 of the gums so that the animals appear to be toothless. In 

 male animals the teeth erupt sooner or later and vary con- 

 siderably in size in the different species ; in old female animals 

 also the tips of the teeth occasionally push through the gum. 

 In addition to these larger teeth, series of very small vestigial 

 teeth are fairly frequently found extending along the gums of 

 upper and lower jaws. As many as 32 have been recorded in 

 one row ; they are relics of an earlier stage in the evolution of 

 these animals when the dentition approximated more closely 

 to that of existing dolphins. 



