The skull in the three families presents modifications partly adapted to their different habits and modes of life, and partly to their race characters. In none, however, do we find the peculiar scissor-like or cutting teeth (see p. 13) of the typical Land Carnivora, but, as in the Bear tribe, the dentition exhibits a diminution in the cutting form of the teeth, and a tendency in some of the creatures to a levelling and conical production of the crown of the molars, while in others these latter show a serrate or saw-like character. For example, in the Walrus all the teeth, save the canines, are short and simple-fanged, the canines themselves, or, as they are more commonly termed in this animal, tusks, being of inordinate length and strength. In the Otariidæ, the canines, though themselves of good size, are small in comparison with those of the Morse tribe, while the incisors and single-rooted molars are more conical and prominent. The dentition of the Phocidæ varies considerably, in some the occasionally double-rooted molars acquiring a tuberculate, in others a saw-like or serrate character, while the incisors are notch-crowned. The bony cavity for the eye is open behind; the facial region is less prominently produced than in some of the feline Carnivora. The region of the brain-pan is relatively full, while the skull, as a whole, is elongated and flat. In youth, the cranium of the Pinnipedia has a predominating brain area, and the entire bony surface is smooth and featureless. As age advances, however, in certain of the genera at least, the relation of parts changes, and the face acquires prominence, while great bony crests arise on the summit and back of the head. The tongue does not possess the spines met with in the Cat tribe, though the surface is roughish. In the Seals, but not in the Walrus, the tip is slightly cleft. The stomach is single-chambered. The intestine is considerably longer than in the Felidæ, averaging fifteen times the length of the body, or thereabouts. The glands of the internal coat in some of the tribe are very extensive, and co-ordinate with the excessively rapid digestion. [Illustration: UPPER SURFACE OF BRAIN OF OTARIA. (_After Murie._)]