1885.] DR. ST. G. MIVART ON THE PINNIPEDIA. 435 



homogeneous, or whether it may have had more than one source. 

 If the latter question can be settled, it then remiiins but to inquire 

 from what source or sources the whole group was derived. 



That the group is subdivisible into three main subgroups has 

 been long recognized. 



Mr. H. N. Turner, in his classical paper on the foramina of the 

 Base of the Skull \ gives to the group the value of a family, P/iocidce, 

 which he subdivides and characterizes as follow " : — 



Fam. Phocid^. 



Molars all similar in structure. 



Subfamily Arctocephalina. 



A postorbital process. An alisphenoid canal ; mastoid process 

 strong and salient, standing aloof from the auditory bulla. 



Otaria. Ar otocephalus. 



Subfam. Trichechina. 



No postorbital process. A distinct alisphenoid canal. Mastoid 

 process strong and salient, its surface continuous with the auditory 

 bulla. 



Trichechus. 



Subfam. Piiocina. 



No postorbital process. No alisphenoid canal. Mastoid process 

 swollen and seeming to form part of the auditory bulla. 



Morunga. Lobodon, 



Cystophora. Leptonyx. 



Halicharus. Utenorhynchus. 



Ommatophoca. Phoca. 



Professor Flower, in his paper on the Classification of the Carni- 

 vora^, says : — "^Yith regard to the group of Seals, which I look upon 

 as essentially belonging to the same ordinal division of the Mammalia 

 as the animals hitherto treated of [i. e. the fissipedal Carnivora], 

 the differences of the cranial characters of the three natural families 

 into which they are divisible, the Otariidce, Trichechidce, and Phocidce, 

 are so well described by Mr. Turner that I need only refer to his paper 

 for them. But I must add that I cannot agree with him when he says, 

 'I have not seen in the Seals anything which, in my opinion, warrants 

 their approximation to any of the other families more than another,' 

 or in his placing them and the three divisions of the terrestrial Carni- 

 vora as primary groups of equal value. The differences between 

 the Seals and the terrestrial Carnivora both in teeth and limbs are 

 much greater than any found between different members of the 

 latter group. They should therefore constitute, in my opinion, a 



1 P. Z. S. 1818, p. 63. 2 L. c. p. 88. = See P. Z. S. 1869, p. 34. 



Proc. Zool. Soc— 1885, No. XXXII. 32 



