Dr. Burmeister observes:—“We have in the Museum [at Buenos Ayres] a young half-grown specimen [of _Arctocephalus falklandicus_] nearly 3 feet long. From this I have taken the skull, of which I send you a description and drawings” (Ann. N. H. 1866, xviii. p. 99, t. 9. f. 1, 2, 3, 4). From the comparison of the figures, and especially of the teeth and the form of the palate, with our older skull of _Arctocephalus Hookeri_, I have little doubt that it is the skull of a specimen of that species before the grinders were all developed. It is not the skull of _Otaria jubata_, which the other specimen he called _A. falklandicus_ is, as proved by the form and position of the hinder nasal openings. The figure of the young skull differs from the older skull of _A. Hookeri_ in the British Museum in having a notch in the middle, while the older skull of _A. Hookeri_ has a conical prominence in the same place. Such differences are found in skulls of Seals at different ages. The skull of the young animal described and figured by Dr. Burmeister as _Arctocephalus falklandicus_ (Ann. & Mag. N. H. 1866, xviii. p. 99, t. 9. f. 1 & 2), is probably the young skull of this species. It agrees with it in the elongated form of the skull, and in the large size and great development of the processes of the orbits. Dr. Murie regards _Otaria Philippii_ as founded on the skull of this species (P. Z. S. 1869, p. 108). Mr. Allen, on the contrary, includes _Otaria Hookeri_ as a synonym of _Otaria jubata_. One could not have a better proof of the want that Mr. Allen had of more materials when he undertook a revision of the family. 4. ARCTOCEPHALUS. Arctocephalus, _F. Cuvier, Peters_. The face of the skull elongate, forehead flat. The palate concave, especially in front, with a thickened margin on each side near the teeth, and then narrowed behind; the internal nasal opening elongate, longer than broad, narrow and arched in front, the edge in a line with the orbital process of the zygomatic arch, which is large and well developed. Flap of toes moderate. In the adult skull of _A. antarctica_, from the Cape, the fifth hinder grinder has only very short rounded callous roots, which are slightly divided into two lobes; and the hinder sixth upper grinder seems to have a root of the same character. But not having any skulls of younger animals, I am not able to describe what are the forms of the roots of these two teeth in the younger state. In the skulls of the older specimens (which are not adult, as they have the sutures between the bones still distinct), the fifth and sixth upper grinders have two distinct diverging roots. * _The fifth and sixth upper grinders with two roots (?); the sixth upper partly behind the hinder edge of the zygomatic arch._ Arctocephalus. (Africa.) 1. Arctocephalus antarcticus. _The Cape Fur-Seal._ Phoca antarctica, _Thunb._, _Mém. Acad. Pétersb._ iii. p. 322; _Fischer’s Synop._ p. 242.