SEXUAL DIFFEEENCES. 39 



systematic writers, who liaye, indeed, no positive information to 

 offer, and very little can be gleaned from other sonrces. All that 

 I have met with, after pretty extensive research, has already been 

 incidentally given in the foregoing acconnt of the external char- 

 acters. All that can be gathered is that in the female the tusks 

 are smaller and thinner, and the general size of the animal may 

 be inferred to be somewhat smaller than in the male. In fact,^ 

 the external characters in the adult animal of the species under 

 consideration have never as yet been given with much detail^ 

 the few naturalists who have met with it in life seeming to take 

 it for granted that an animal so long known, and so familiar to 

 them, must be well known, thereby rendering a careful and de- 

 tailed description unnecessary. The very good descrii)tion given 

 by Dr. Gilpin (see antea, pp. 31, 32, 33) of an adult is about all 

 that I have met with in the way of detailed descriptions of the 

 adults of either sex. 



The figures and descriptions given of the young, especially 

 those recently published by Dr. J. Murie,* leave httle to be desired 

 as regards the external characters in early life. The absence of 

 references to any strongly marked sexual differences in the 

 adult might perhaps be taken as negative evidence that none 

 exist ; but on the basis of analogy with the other Pinnipeds, 

 especially with the Otariidce, we should hardly expect their 

 absence. Even in the case of the skulls, few sexed specimens 

 appear to have come under the observation of specialists. We 

 here and there, however, meet with references to supposed sex- 

 ual differences in the size and character of the tusks, and also 

 in respect to the size of the skull and the density" and weight of 

 the bones in those of supposed females as compared with those 

 of supposed males. Thus, Wiegmann, in 1832, in referring to 

 the species described by Fremery, in 1831, says, in remarking 

 upon Fremery's " Trichechus CooJcii,''^ that he remembers having 

 heard from a Greenland traveller that the female Wabus has 

 longer and slenderer tusks than the male, and states, on the au- 

 thority of Fremery, that a young specimen in the Eoyal Museum 

 of HoUand, having long, slender tusks, was regarded by Tem- 

 minck as a female. He also considers, on the gTound of analogy, 

 that the greater or less development of the occipital and other 

 crests of the skull, as well as the relative weight of the bones, 



* " Researches upon the Anatomy of the Pinniipedia. Part I. On the Wal- 

 rus (Tiichechus rosmarus, Linn.)." Trans. Zool. Soc. LoncL, vol. vii, 187'2, j)p. 

 411-464, with -woodciits, and ijlates li-lv. 



