VARIATION WITH AGE. 287 



SEXUAL DIFFERENCES. From the testimony of Captain 

 Scammon, and from the material I have been able to examine, 

 the female differs from the male in color in being rather lighter, 

 or of a more yellowish-brown. The most notable difference is 

 in size, the female being very much the smaller, but not quite 

 so great a sexual disparity in size obtains in this species as 

 in Eumetopias stelleri and Callorhinus ursinus.* Unfortunately 

 the material at ray command will not enable me to give full 

 statistics on this point. Most of the male specimens in a large 

 series sent to the Museum of Comparative Zoology, by Mr. 

 Schumacher, from Santa Barbara Islands, are young or middle- 

 aged, only one having the teeth perceptibly worn or the crests 

 of the skull very highly developed. A comparison of very old 

 skulls of both sexes shows that nearly the usual amount of sex- 

 ual variation in size common to the Otaries obtains in the pres- 

 ent species. The table of measurements (on page 285) of ten 

 skulls five male and five female all fully adult and most of 

 them very old, gives all the information I am able to offer re- 

 specting sexual variation in size. 



As usual in this group, the dental armature (especially th& 

 canines and caniniforni incisors) is much weaker in the female 

 than in the male, by means of which the skulls of females can 

 be readily distinguished from those of males of about the same 

 size. The whole skull is slighter and weaker, and all the pro- 

 cesses and ridges for the attachment of muscles much less devel- 

 oped. There are, however, in very old female skulls, distinct, 

 but comparatively low, and thin sagittal and occipital crests, 

 which attain the height of 3 to 6 mm., while in the males they 

 sometimes rise to 35 or 40 mm. The limbs are also much weaker 

 and slenderer, as of course are all the bones of the skeleton. 



VARIATION WITH AGE. As already noticed, the color of the 

 young at birth is dark gray or slaty, and the pelage has at this 

 time a delicate softness, due to the silky texture of the hair. 

 The pelage is wholly devoid of a second coat of true under-fur, 

 like that of the Fur Seals, but from its softness might readily 

 be mistaken on casual observation for true fur. This is verj^ 

 soon replaced by a coarser and harsher, but still quite soft 

 pelage, in comparison with that of adults, of nearly uniform 

 chestnut or dark reddish-brown color. This is succeeded by the 

 harsh, stiff pelage of the middle-aged and adult animals. 



*Seenfed,p. 226. 



