INTRODUCTION. 



The PiNNiPEDiA are aquatic mammals, with few exceptions marine, 

 living in the water, in which they obtain tlieir food, either fish, 

 molluscs, or Crustacea, but resorting to the land for breeding and 

 bringing forth their young, and at times basking on the rocks or on 

 the ice. From their aquatic habits, the limbs are modified in shape 

 and to some extent in structure so as to be adapted for swimming 

 and diving They have an extensive distribution in the great oceans, 

 Atlantic and Pacific, and in the smaller communicating seas. Many 

 species are found in the Arctic, and others again in the Antarctic 

 region. 



The Pinnipedia are a suborder of the Carnivora. They are 

 appropriately classed in three well-marked families : the Trichecidse 

 (Odobaenidfe), the Walruses ; the Otariidee, Arctocephalidte, the Eared 

 8eals ; the Phocidte, the Hair Seals, without a pinna to the ear. 



I may refer to my Report on the Seals collected during the voyage 

 of the Challenger {Report, part Ixviii., 1887) for a more detailed 

 description of the anatomical characters of the skeletons and skulls, 

 not only of the specimens collected by the naturalists on the 

 Challenger, but of the Pinnipedia which frequent the North Atlantic, 

 Arctic and Antarctic Oceans, examples of which are in the Museum. 



The Trichecid^ amongst existing mammals consist of only a 

 single genus, Trichecus (Odobaenus). Authorities generally con- 

 sider that the genus contains only the species Trichechus rosmarus. 

 Mr J. A. Allen, however, contends that the Walrus of the North 

 Pacific differs from that of the North Atlantic, and he applies to the 

 former the specific name T. obesus. It seems doubtful if the 

 anatomical differences which he has noted in the comparison of 

 skulls from the North Pacific and North Atlantic should be regarded 

 as having specific distinction. I have found, in the study of the 

 crania in the Museum from the North Atlantic, differences not 

 unlike those to which Allen has attached specific importance, 

 obviously due to the stage <»f development of the canine tusks, 

 their length, thickness, and curvature, which modify the projection 

 and breadth of the face, and are sexual or individual variations, and 

 not of specific importance. The Walrus is an Arctic animal, but 

 stragglers have been captured in Orkney and the Hebrides. 



161 11 



