Eumetopiina, _Gray_, _Ann. & Mag. N. H._ 1869, iv. p. 269. 7. EUMETOPIAS. Eumetopias, _Gill_, _Peters_. Arctocephalus § _a_***, _Gray_, _Cat. Seals & Whales_, p. 51. Fur without any under-fur. Palate flattish or rather concave in front, as wide in front as at the end of the tooth-line, and then slightly narrowed behind. Posterior nares oblong, elongate, broadly truncated in front, the front edge being behind the line of the orbital process of the zygomatic arch. The grinders have large oblong roots; the second, third, and fourth upper ones have a subcentral longitudinal groove on the outer side, and a less marked one on their inner surface; the inner side of all but the first of the lower ones are similarly grooved; the fifth upper grinder (or, more properly, the sixth in the normal series) has two distinct roots. The lower jaw much more elongate than that of _Otaria jubata_, the hinder angle more oblique, and the lower margin long and straight. Flap of toes short. The skull of the young animal, which was sent by Mr. A. S. Taylor to Mr. Gurney from California, and which I first described, with doubt, as _Arctocephalus monteriensis_, junior (P. Z. S. 1859, p. 357), and which in the ‘Catalogue of Seals and Whales’ I named _A. californianus_ (see p. 51), agrees in every respect in its dentition with the large skull which we received from California, and which I described and figured as _A. monteriensis_ (P. Z. S. 1859, p. 358, t. 72); but it differs greatly in the form of the hinder nares, which are extended much more forwards, so that the front end, which is very narrow and acute, is much in front of the prominence of the orbit of the zygomatic arch, being, in fact, about in a line with the middle of the lower edge of the orbital cavity. This skull is evidently that of a very young animal; for the bones are separate; but it has the same number and disposition of the teeth as the large skull. There is the same wide space between the fourth and fifth upper grinders; but there is at the back edge of the fourth grinder, on the right side of the skull, a small pit, from which, no doubt, a small rudimentary tooth has fallen out; and there is a much wider but shallow pit on the other side, which may have been produced by the loss of a rudimentary tooth; the last upper grinder has a large swollen undivided root. If this is a young skull of _Eumetopias monteriensis_, that species is curious for having the teeth in the old and young skulls in the same situation as regards the bones of the face. The adult skull and the young one were from the same locality, and, I believe, collected by the same person; and this being the case, I am inclined to regard them as the same, only showing a curious peculiarity in the growth of the animal, and also showing that the form and position of the hinder nostril probably varies as the animal increases in age.