EVOLUTION OF WHALES 



317 



(Fig. 101, //), while the jaws have become greatly elongated. The 

 teeth have in some cases completely disappeared, as in the whale- 



FIG. 162. Skull of the Dolphin, x J. (From British Museum Guide.) 



bone whales (except for foetal vestiges), while in others they are 

 present in large numbers but have lost the typical mammalian 



FIG. 163. Dorsal and lateral views of the Skull of a primitive Whale, 

 Prozeuglodon atrox, X rV (From British Museum Guide.) 



differentiation into incisors, canines, premolars and molars, being 

 represented by a continuous and uniform series, all of which are 

 conical in shape and single-rooted. Such teeth occur in both 



