BULLETIN OF THE 71 



According to Peters, the length of the skull of 0. Gillespii is 295 mm. ; 

 of one of the skulls of 0. japonica (Schlegel MS. = 0. Stelleri of the Fauna 

 Japonica) is 270 mm. and of the other 310 mm., which would indicate 

 an animal f about three fourths the size of E. Stelleri. 



If we can assume that the California " lion marin " of Choris * is this 

 species, which we can hardly do with certainty, it differs from the E. 

 Slelleri in being browner and smaller, with a more delicately shaped head 

 and uarker mustaches. The latter, however, are variable in color, in other 

 species, in specimens specifically the same. 



Individual Variation. — The two male skulls of Zalo/ihus Gillespii before 

 me differ from each other very remarkably in various points. Besides 

 the general difference in size indicated in the above table of measure- 

 ments, there are other and more radical differences in proportions and form. 

 In the specimen received from the Chicago Academy, the general form is 

 much more elongated than in the other, especially the facial portion of the 

 skull and the postorbital cylinder. The nasals are especially longer, and 

 the expanded interorbital space shorter, with the postorbital processes 

 much more heavily developed. The brain-box, seen from above, through 

 the gradually sloping postorbital constriction, is triangular, whilst in the 

 other, through the abruptness of the postorbital constriction, it is quadrate. 

 Hence in the latter the brain-box has distinct latero- anterior angles, whilst 

 in the other the lateral walls of the brain-box gradually and regularly con- 

 verge anteriorly. The differences in these respects are far greater than 

 exist between the two male skulls of Callorhinus ursinus represented in 

 Plate II. The following proportions indicate the extent of the difl'eiences 

 seen in the form of the postorbital cylinder. 



The diameter of this part, at its point of greatest constriction, in the 

 specimen received from the Smithsonian Institution is 23 mm. ; do. of 

 the specimen received from the Chicago Academy of Sciences, 35 mm. 

 The length of the postorbital cylinder in the first is 43 mm. ; in the lat- 

 ter, 69 mm., or nearh/ one and a half times longer than in the other; 

 whilst the difference in the whole length of the skull in the two speci- 

 mens is less than one seventh of the length of the smaller specimen. 

 Species, and even genera, have been based on differences of less impor- 

 tance than these. 



General Remarks. — Schlegel, in the work above cited, gave the first 

 and thus far the fullest account we possess of this species. lie also 

 gave figures of several skulls, of a skeleton, and of a middle-aged female. 

 He failed, however, to distinguish this species from the Z. hbatus and 

 the Eumetopias Stelleri, but confounded the three under the name Otana 



* Voyage Pittoresque (lies Ale"ontiennes, p. 13). 



