VARIATIONS DEPENDENT UPON AGE, ETC. 



43 



conjectures of Wiegmanu and Temminck. Wliat other differ- 

 ences obtain, especially in external characters, can as yet be 

 only conjectured. It is to be hoped, however, that we shall 

 not have long to wait for detailed accounts of the external 

 characters of the adults of both sexes. 



Fig. 3. Odobamus rosmarus, 9 



Indxyidual Vaeiations, and Yariations dependent 

 UPON Age. That a wide range of individual variation obtains 

 in this species is sufficiently evident from an examination of 

 even a limited series of skulls. These differences have been 

 noted in considerable detail by Fremery, Wiegmann, Stannius, 

 and Jaeger, as will be presently noticed more in detail in pre- 

 senting the general history of the species. StiU greater differ- 

 ences, of course, result from differences of age. These collect- 

 ively, as win be noted later, have formed the basis of several 

 nomiual species. AU the Pinnipeds appear to be subject to a 

 wide range of variations of this character, and none more so than 

 the Wakuses. These affect to a considerable extent the general 

 proportions of the skull, and especially thfe form and relative 

 development of different bones. These latter differences are 

 best seen in comparatively young skuUs, since most of the 

 sutures close at a rather early age. Among these variations 

 are especially noteworthy those of the nasal bones, the iuter- 

 maxiUaries, and the frontals, and to a less degree those of the 

 base of the skull. The crests and ridges for muscular attach- 



