32 BULLETIN OF THE 



Of the Sexual, Age, and Individual Variations. 



Sexual Differences. — "Whilst in the carnivores generally the sexual 

 variations are considerable, especially in respect to size, they seem 

 to never exist in greater degree than in the Otariadce. In all the 

 species of this family in which the sexes are well known, — especially 

 in Otaria jubata, Eumetopias Stelleri, Callorhinus ursinus, and Arcto- 

 cephalus falklandicus, — it has been found that the weight of the adult 

 females is rarely above one sixth' to one fourth that of the old males ; 

 — a sexual disproportion in size rarely if at all elsewhere met with 

 in mammals. Iu the Pinnipedes the nearest approach to it is in the 

 sea elephant (Macrorhinus elephantinus), which in some of its habits, as 

 previously mentioned, also approaches nearer to the eared seals than 

 any other well-known species of the Phocidcc. 



The sexes differ also in color, the females being generally much 

 lighter colored than the males. 



They also differ in the size of the teeth, especially of the canines, the 

 females having relatively, as well as absolutely, much smaller teeth 

 than the males. The form of the palatal surface of the maxillaries 

 also varies in the two sexes in the females it being usually flatter or 

 less depressed than in the males, and its lateral outlines straighten 

 The females also lack the high crests of the skull possessed by the 

 males, and have the processes of the bones less developed. 



One of the greatest sexual differences, however, is seen in the pelvis. 

 In the female it is much smaller than it is in the male, and the pubic 

 bones instead of meeting behind, as in the males (and also in the females 

 in the P/iocidce), are widely separated, and with the i-chia are re- 

 duced to a slender rim enclosing the large thyroid foramen; at least this 

 is the ease in Callorhinus ursinus, and there seems to be no reason for 

 believing that similar differences in the structure of the pelvis do not 

 exist in the other species of the Otariadce.* 



* Respecting the sexual differences in the Otariajubata, Dr. G. A. Maack lias fur- 

 nished me with the following note: — 



"The most striking feature in Olaria jvbata i< tin- great dissimilarity between the 



males and females, not only in res] t to size and general external features, but also in 



their osteological structure. It is a curious fact, that, whilst the male changes greatly 

 with age in respect to its osteological characters, the female prssents in this respect a 

 greater or less constancy of character. In color, however, tin' reverse obtains, — the 

 males preserving a greater constancy in this respect, whilst the females vary exceed- 

 ingly at different ages." 



