SPERM WHALES AND BOTTLE-NOSED WHALES 259 



only to be found on the lower jaw ; and " Physeter " , from the 

 Greek for a blowpipe, alludes to the single external breathing 

 aperture with which the animal is provided. 



Its external form makes it impossible for the Sperm Whale 

 to be confused with any other species of Cetacean, whether 

 toothed or not. It resembles a gigantic tadpole in that the 

 most massive and conspicuous part of the body is the head, 

 which comprises about one-third of the total length. The 

 greatest body circumference is situated in the region between 

 the eyes and the flippers, and from this point the body tapers 

 backwards towards the stock of the tail, and forwards, in a 

 lesser degree, to the front end of the blunt rounded head. 



The head is not as box-shaped as it is frequently represented 

 in pictures, and if a section were cut at right angles to the long 

 axis just in front of the tip of the lower jaw, which, it will be 

 remembered, does not extend to the front of the head, it 

 would be seen that the upper surface is rounded off evenly to 

 the sides. These are not quite flat, but each has a concavity 

 which, seen in the head as a whole, is a depression running 

 longitudinally, deepest near the front and fading out gradually 

 as it passes backwards. Below this concavity the sides 

 approximate to each other and meet at an acute angle, recalling 

 in form that of the keel of a ship. The single external aperture 

 of the blowhole is situated on the left side near the front of the 

 head. 



The lower jaw, although by itself it looks powerful enough, 

 seems disproportionately small in the living animal when 

 compared with the massive head. It may be described as 

 v-shaped, having the ends of the two branches articulating 

 with the skull and the stem forming the tooth-bearing free 

 end. The number of teeth on either side of the lower jaw is 

 variable and may range from 18 to 28, nor need the number 

 on either side be equal. The teeth are large and powerful, 

 firmly fixed in the jaw-bone, conical in shape when unworn, 

 and frequently attaining a length of over 8 inches. When the 

 mouth is shut the points ot the lower jaw teeth are accommo- 

 dated in sockets in the strong fibrous tissue of the palnte, so 

 that even without functional teeth in the upper jaw very 

 adequate provision is made for retaining the food. A few 

 vestigial teeth, an inch or two in length, are sometimes to be 



