60 BULLETIN OF THE 



The palatine bones seem to be particularly liable to vary in length and 

 form on the two sides of the same skull, as does also the position of the 

 last molar tooth. On the left side the distance between the fourth and 

 fifth molars in the older skull is 3."> mm., on the right side 26 mm. 



In the younger skull the left side is also just appreciably more devel- 

 oped than the right. In the older individual the asymmetry is readily 

 traceable throughout the skeleton, in the hind feet especially, the one 

 being much larger than the other. 



General Remarks. — The northern sea lion was first described by 

 Steller in 1751, who, under the name of Leo marinas, gave a somewhat 

 detailed account of its habits and its geographical range, so far as known 

 to him. His description of the animal, however, is quite unsatisfactory. 

 Steller's Leo marinus, in size, general form and color, closely resembles 

 the southern sea lion (Otariajubata), with which Steller's animal was 

 confounded by Pennant, Buffon and nearly all subsequent writers for 

 nearly a century. Peron, in 1816, first distinctly affirmed the northern 

 and southern sea lions to be specifically distinct. Lesson, in 1828, gave 

 it the specific name it now bears, in hpnor of Steller, its first describer. 

 The following year Fischer, on the authority of Lesson, also recognized 

 its distinctness from the southern species. Nilsson, in 1840, in his cel- 

 ebrated monograph of the seals, reunited them. Midler, however, in an 

 appendix to Dr. W. Peters's transition of Nilsson's essay, published in 

 the Archiv fur Naturgeschichte for 1841, separated it again, and pointed 

 out some of the differences in the skulls that serve to distinguish the 

 two species. Gray, in his Catalogue of the Seals published in 1850, 

 also regarded it as distinct. But one is led to infer that he had not yet 

 seen specimens of it, and that he rested his belief in the existence of 

 such a species mainly on Steller's account of it, as he himself expressly 

 states in his later papers. The ^kull received subsequently at the Brit- 

 ish Museum from Monterey, California, and figured and described by 

 Gray as a new species, under the name of Arctocephalus monteriensis, 

 proved, however, to be of this species, as first affirmed by Dr. Gill, and 

 later by Professor Peters and Gray himself. With the exception of the 

 figures of an imperfect skull of Steller's sea lion from Kamtchatka, given 

 by Pander and D' Alton in 1826, Dr. Gray's excellent figure (a view 

 in profile) is the only one of its skull hitherto published. The only 

 specimens of the animal extant, up to a recent date, in the European 

 museums, seem to have consisted of the two skulls and a stuffed skin in 



