226 



FAMILY OTARIID^. 



considerable range of individual variation in representatives 

 of the same species, so that coloration alone fails to afford sat- 

 isfactory diagnostic characters. All the Fur Seals are black 

 when young, but they become lighter with age, through an 

 abundant admixture of grayish hairs which vary from yellow- 

 ish-gray to whitish-gray. The southern Fur Seals are generally, 

 when adult, much grayer than the northern. There is hence a 

 wide range of color variation with age in the same species, as 

 there is also among conspeciflc individuals of the same sex and 

 age. While some have the breast and sides pale yellowish-gray, 

 others have these parts strongly rufous, the general tint also 

 showing to some extent these differences. 



There is also a wonderful disparity in size between the sexes,* 

 the weight of the adult males being generally three to five 



* The sexual diiference in size varies only slightly iu the dilferent genera : 

 it is greatest, apparently, in Otaria, and least iu ArctocephaJus. It is very 

 much less in Arctoceplialus australis than in the northern Fur Seal ; while 

 relatively small in Zalophus, it is very great in both Otaria and Eumetopias. 

 In Otaria jiibata, the average dimensions of eight old male skulls are, length 

 350 mm. , breadth 223 mm. ; of four old female skulls, length 261 mm. , breadth 

 143 mm. In Eumetopias stelleri the average length of ten old male skulls is 

 375 mm., breadth 221 mm. ; of two old female skulls, length 296 mm., breadth 

 157 mm. In Zalophus californianus very old male skulls obtain a length of 

 290 mm. to 330 mm., while very old females reach 220 mm. to 237 mm. Five 

 old male skulls average, length 269 mm. , breadth 157 mm ; five old female 

 skulls, length 219 mm., breadth 103 mm. In Arctocephahts australis two old 

 male skulls average, length 260 mm., breadth 145 mm., two old female 

 skulls, length 230 mm., breadth 121 mm. In Callorliinus ursinus eight adult 

 male skulls (not generally very old) average, length 243 mm., breadth 123 

 mm. ; four female skulls of nearly corresponding age average, length 188 mm., 

 breadth 96 mm. These data may be tabulated as follows, 100, in the column 

 of ''Approximate ratio," representing the male sex : 



Species. 



otaria jubata 



Do 



Eumetopias stelleri 



Do 



Zalophus califomianns . 



Do 



Arctoceplialus australis 



Do 



Callorhuius ursinus 



Do 





d 

 ? 

 d 

 ? 

 d 

 ? 

 d 

 ? 

 d 

 ? 



8 



4 



10 



2 



5 



5 

 2 



2 

 8 

 4 



a 



350 

 261 

 375 

 296 

 289 

 219 

 260 

 230 

 243 

 188 



OS 



o 

 u 

 M 



Approximate ratio. 



223 

 143 

 221 

 157 

 157 

 103 

 145 

 121 

 123 

 92 



> =69-100. 



Length 75-100) 



Breadth 64-100 



Length 79-100 ) 



> =75-100. 

 Breadth 76-100 5 



Length 81-100 )^^joo_ 



Breadth 66-100 i 



Length 88-100 >g5_jQQ_ 



Breadth 83-100 > 



Length 77-100 j^g,^,)^ 



Breadth 75-100 > 



