The oldest of the three adult skulls in the British Museum differs from the other two in the pterygoid processes of the hinder edge of the palate being closer together than in the rest; but this character seems to depend on the greater age of the animal, as it differs slightly in the other two specimens. In all the younger specimens, varying greatly in size, the pterygoid processes are far apart. Dr. Peters considers (1) _Platyrhynchus leoninus_ of F. Cuvier, (2) _Phoca Byronia_ of Blainville, and (3) an adult specimen which is in the Hamburg Museum, and of which he described and figured the skull as _O. Godeffroyi_, to be distinct species. I cannot see any difference between the skull in the College of Surgeons, on which _Phoca Byronia_ was founded, and those in the British Museum; and the figure of the skull described as _O. Godeffroyi_ is very similar to the skull in the British-Museum collection which I have called _O. jubata_. This animal has the harsh fur without any under-fur of _Phocarctos Hookeri_; but it entirely differs from that animal in the colour of the fur. This cannot arise from the greater age of the animal, as it is not nearly so large as the half-grown _P. Hookeri_ in the British Museum. In the dark blackish-brown colour of the fur and the pale-brown colour of the nape, and in the absence of the under-fur, this Seal resembles the adult _Neophoca lobata_ from Australia; but in that species the pale colour extends all over the crown, while in the young male _Otaria jubata_ there are only a few paler scattered hairs on the middle of the crown and nose. Dr. Murie represents the skull of a nearly full-grown male and of a female nearly of the same age (P. Z. S. 1869, p. 103. f. 1, 2). They greatly differ, the nose and the palate being much wider in the male than in the female, and the teeth in the male (but this may be only an individual peculiarity) were much worn down. He observes, “the whole of the palate is much narrower than in the male of the same size, especially in the maxillary region, and the teeth are much weaker and more sharply pointed.” He observes, “The young of both sexes are alike of a dark brown or very deep chocolate colour. The males about a year old retain somewhat of the chocolate tint of their youth, which, however, is paler, and subsequently changes annually as the coat is shed. The females of equal age assume a dark grey hue dorsally, while the abdominal parts are light yellowish. As they grow older they alter little. “Males a couple of years old or more become of a rich brown shade on the back and sides, and lighter or yellowish beneath. Old males alone are maned. “There is a sparse underwool on the young, which sensibly diminishes with age. “The skulls of the adult male and female differ considerably, the latter being comparatively the narrower of the two—the former possessing a somewhat different form of teeth, besides proportionally immense canines.