MONOGEAPH OF THE PINNIPED ES. 11 



This family, especially developed in the Pacific, is rep- 

 resented by several genera, which may be distinguished as 

 follows : — 



I. Palatal surface of maxillaries extending behind the teeth, and with 

 its posterior processes very long. Bony palate extending nearly to the 

 pterygoid processes and truncated or convex behind. Otaria.* 



II. Palatal surface of maxillaries at middle not extending beyond the 

 grinders, and with moderate lateral extensions. Bony palate very deeply 

 emarginated. 



a. Face high, boldly decurved and shorter than orbit. Molars 3-; 

 approximated, compressed, conic. 



AECTOCBPHALUS.t 



b. Face produced, longer than orbit. 



1 . Molars j ; last upper far behind the inner margin of orbit. 

 Posterior nares very high and narrow. Bony palate with a very narrow 

 emargination, notched at suture. Forehead very thick and tumid, with a 

 triangular flattened area. Postorbital processes quadrate. Eumetopias. 



2. Molars ^; approximated ; last under zygomatic process ; poste" 

 rior nares wider than high behind. Bony palate with a continuous concave 

 emargination behind. Forehead, depressed, with triangular postorbital 

 processes. Occipital crest very high. Zalophus. 



3. Molars 5- ; lower more or less trilobate ; last upper behind in. 

 iier margin of zygomatic process. Halakctus. 



ROSMARID^. 



The Walrusses have a very robust body, and no external 

 ears. The skull provided with " no postorbital processes ; 

 a distinct alisphenoid canal ; mastoid process strong and 

 salient ; its surface continuous with the auditory bulla " 

 (Turner). Incisors deciduous; the external on each side 

 being alone retained in the gums. Canines extraordinarily 



* Otaria is said by Dr. Gray, in bis last enumeration of the family, to have " the 

 palate very concave, decurved deeper with age, ^c." I cannot understand such a state- 

 ment with regard to the bony palate ot Otaria leonina, and consequently describe 

 the appearance of the bones as they appear to me, 



t As I have known it to be suggested that the A. monteriensis and A. Gittiespii 

 may be identical, it may be proper to state that the first is not found in the South, 

 where the other species dwell, although the second may inhabit the same regions in 

 the North. The differences between the three species are so great, that it may be al- 

 most a matter of surprise that they should not have been generically separated be- 

 fore. I have examined the complete skeleton and three skulls of adults of A. 

 monteriensis ; the skull of a very old male of A. Gilliespii ; and skulls of live young 

 epecimens of A. ursinus, besides part of the skeleton. 



