Mammalia. 1 1 



variable number of, it is true, rudimentary claws on the hind- 

 tlippers of each species. 



It seems improbable that we shall ever approach more nearly to 

 an understanding of the true inter-relationships of the Phocidae until 

 we discover some of the ancestral forms from which they have 

 sprung.^ Possibly the various genera left the ancestral tree at various 

 epochs, and, if we are to follow Sir William Flower, we have in 

 Macrorhinns the most highly specialised form of the whole group. 



As to the StenorhyncMnae, they must be regarded as the 

 descendants of an ancestor which became isolated from the pre- 

 cursors of the remaining two sub-families at a sufficiently early 

 period to allow of the formation of the various distinct genera which 

 now exist. The exact relationships of these amongst themselves 

 cannot, I think, be more clearly indicated than has been attempted 

 above. Ommatophoca is certainly the most distinct, and may be 

 regarded as annectant between the StcnorhyncMiiac and Oysto'pliorinae. 

 If any convenient result would accrue therefrom, it might be taken 

 to constitute a separate sub-family, the Ommatojphocinae, but I do 

 not see how the multiplication of sub-families can help us much. 



A certain amount of light on the origin of some of the genera 

 may, perhaps, be derived from the young. Thus the young of 

 Halichcerus, a genus which has not at the present day an Arctic 

 habitation, are white (or nearly so), thereby perndtting the suspicion 

 that its ancestors were of Arctic origin, or, at least, dwellers in regions 

 where the cold was more intense than those which they at present 

 frequent. On the other hand, the only Seal of the Antarctic, which 

 is nearly white, is Lobodon, and its mottled young suggest a com- 

 paratively recent inroad of the species into the cold regions of 

 the South Polar area. 



It is interesting to find the teeth of Phoca hispida paralleled in 

 the south by those of Oymorhinus, while the teeth of Leptonychotcs 

 recall those of P. vitulina, and Monachus, in this respect to a certain 

 extent, resembles Halichcerus. 



Dentition. — The teeth of the Phocidae are remarkable for the 

 extreme variation which they display in the genera. In most cases 

 dental characters present the most distinct features between animals 

 which are externally very similar. In the skins, as seen in museums, 

 Leptonychotes and Lohodon are, but for their colour, difficult to 

 separate, yet nothing could be more distinct than the forms of their 



^ Stenorhynchua vetus of Leidy is so close to (if not identical with) Lohodon 

 carcinojjkaguH thai it affords us uo lulp whatsoever. 



