Mr. Gill considers Steller’s Sea-bear (_Callorhinus ursinus_) to be the type of M. F. Cuvier’s genus _Arctocephalus_, and therefore abolishes _Callorhinus_ and gives the new name of _Halarctus_ to the true _Arctocephali_—thus unnecessarily adding to the confusion of the generic names of these animals. He fell into this mistake by not observing that _Phoca ursina_, and even _Otaria ursina_, had been applied to several species from very different localities, that F. Cuvier established his genus on the skull of _P. ursina_ of Forster, from the Cape, which he (M. Cuvier) had named _Phoca Delalandii_, and that F. Cuvier does not figure a skull of the Sea-bear of Steller: indeed the French collection did not at that time, nor does it even now, possess one; and I feel assured that, if it had, F. Cuvier would, according to his custom, have established for it a genus distinct from _Arctocephalus_, the skulls of the two genera being of such distinct forms. 1. Eumetopias Stelleri. _Northern Sea-lion or Fur-Seal._ Arctocephalus monteriensis, _Gray_, _Cat. Seals & W._ p. 49; _P. Z. S._ 1859, t. 72 (skull). Eumetopias californiana, _Gill_, _Proc. Essex Inst._ 1866, v. p. 13. Otaria Stelleri, _Gray_, _Cat. S. & W._ p. 60; _Peters_; _Müller_? Otaria (Eumetopias) Stelleri, _Peters_, _Monatsb._ 1866, pp. 274 & 671. Eumetopias Stelleri, _Gray_, _Ann. & Mag._ 1866, vol. xviii. p. 233; _Allen_, _Bull. Mus. Comp. Zool._ vol. ii. pp. 44, 46, tab. 1 & 2 (skull &c.). Leo marinus, _Steller_. Phoca jubata, _Pander & D’Alton_, t. 3. f. _d_, _e_, _f_ (skull, not good). _Junior._ Arctocephalus californianus, _Gray_, _Cat. S. & W._ p. 51 (skull only). Inhab. California; Behring’s Straits. The skin of the young specimen which Mr. Gurney gave to the Museum along with what was said by Mr. Taylor to be its skull (see ‘Cat. Seals & Whales,’ p. 51) was the only skin then known to exist in museums; and consequently I described the fur of the genus from this skin as having abundant under-fur (see Proc. Zool. Soc. 1859, p. 358). Dr. Peters having discovered Pander and D’Alton’s animal and skull in the Paris Museum, he observed that the adult animal was entirely without under-fur—a fact which has been confirmed by Mr. Allen, who suggests that the skin of the young received from Monterey is the skin of the young _Eumetopias Stelleri_, which, I think, is very probable. But this only shows the difficulties that must occur in the study of animals from the very imperfect materials which until lately existed.