174 A BOOK OF WHALES 



Broadly speaking it would seem likely that the 

 Mystacoceti were to be derived from the Odontoceti, 

 and not vice versa, if only on account of the teeth 

 visible in the embryos of the toothless whales. On 

 this view we might look upon those toothed whales 

 in which the teeth are diminishing as the nearest 

 approach among the Odontocetes to a Mystacocete. 

 In this case it is clear that the Ziphioids would 

 occupy that position, for it is in that group that the 

 teeth are poorest in their development. But there 

 is no hint in any of them of appearing whalebone. 

 Neither can any other definite structures be laid hold 

 of which support considerations derived from the 

 dwindling teeth. It seems too trivial a matter to 

 raise the question of the nearly perfect symmetry 

 of the skull of Berardius, and of the distinct lacrymal 

 and malar bones in the Ziphioids as well as in the 

 Right whales. The fact seems to be that the meeting- 

 point between the two great divisions of the whale 

 tribe, if there is such a meeting-point, and the group 

 is not diphyletic, is to be sought for no nearer than 

 in the Eocene period among the Zeuglodonts. 



And yet there are other considerations which seem 

 to suggest that a renewed search for affinities between 

 the two groups among more recent forms should 

 produce some result. In contradistinction to the 

 Odontocetes the whalebone whales are a limited group, 

 which, as is pointed out here (p. 119), are so closely 

 related one genus with another, that it is really 

 difficult to form them into more than one family. 

 This suggests a recent origin ; for in groups, which 



