326 CALLORHINUS URSINUS NORTHERN FUR SEAL. 

 Measurements of the Skeleton Continued. 



* Fore Umb. 



t Hind limb. 



Sexual Differences. The sexes differ in color, as already 

 stated, in the females being much lighter than the males, or 

 grayer. In respect to the skeleton they differ extraordinarily 

 in the form of the pelvis, as already described, all the parts of 

 which in the female are greatly reduced in size, and instead of 

 the pubic bones meeting each other posteriorly, as they do in the 

 males, they are widely separated. The innominate bones are 

 also much further apart in the females, and the bones forming 

 the front edge of the pelvis are less developed, so that the pelvis 

 in the female is entirely open in front. In consequence of the 

 remarkable narrowness of the pelvis in the male, the form of 

 this portion of the skeleton is necessarily varied in the female, 

 to permit of the passage of the fcetus in parturition. As already 

 remarked, no such sexual differences are seen in the Phocidw. 



In respect to other parts of the skeleton, the absence of the 

 great development of the sagittal and occipital crests seen in 

 the males has already been noticed. The bones of all parts of 

 the skuU are much smaller and weaker, especially the lower 



