So A BOOK OF WHALES 



Seen from the ventral surface the whale's skull 

 is quite symmetrical ; this is the case even with 

 Kogia and Physeter, which are the most asymmetrical 

 of whales above. It is important to note that in the 

 foetus the asymmetry is less marked than in the 

 adult. This leads us to the conclusion that the 

 singular deformity of the head which characterises 

 the toothed whales is, at least comparatively speaking, 

 a new development. 



The whale's skull also offers us an excellent instance 

 of how great a departure from the typical appearance 

 of an organ may be produced without any real change 

 in its structure. There are no bones in the skull that 

 are not found in other mammals, and none of the 

 bones found in other mammals are wanting ; and yet 

 the skull as a whole departs widely in general appear- 

 ance from that of other mammals. 



The brain case proper is relatively small (see Figs. 

 19, 20, pp. 1 1 8, 119), and the snout, the facial portion 

 of the skull, is very elongated, the degree of elongation 

 varying from genus to genus. It is most developed, 

 perhaps, in the extinct Eurhinodelphis (apparently a 

 Platanistid), of which a figure is appended. The 

 toothed whales, in fact, embody the extremes of 

 shortening and elongation of the facial region of the 

 skull. Thus it is very short in Orcella, in Kogia, and 

 in a few others. 



Several of the individual bones show peculiarities, 

 of which some will be mentioned in the present 

 general account of the whale's skull. The parietals 

 deserve their name, for they are really walls to the 



