56 BULLETIN OF THE 



relative length of the bony to the. cartilaginous portions, in the older the 

 ossified portion being much longei and the cartilaginous much shorter than 

 in the other. An irregularity will be also observed in respect to the ster- 

 nal segments, the younger specimen having a supernumerary cartilagi- 

 nous one between the 8th and 9th normal ones. 



Age and Sexual Variations. — In regard to the present species my ma- 

 terial does not furnish many facts in respect to these points, since the two 

 males contained in Captain Bryant's collection constitute at present my 

 only resources. These examples, he writes me, were selected " as average 

 specimens of full-grown males, but in the selection," he says, " we were 

 governed somewhat by the desire to have skins perfectly haired, many of 

 the animals being chafed by the rocks, even to having sores." " I should 

 estimate," he further adds, "the age of one of them to be nine or ten 

 years, that of the other fifteen." These specimens, however, differ consid- 

 erably from each other in color, size, and proportions. Some of these dif- 

 ferences are clearly due to age, but others equally great cannot be thus 

 explained. These specimens show that the body increases greatly in bulk, 

 and the bones in size and density, after the animal has reached its adult 

 length. The crests of the skull are almost wholly developed after this 

 period, and in great measure also the spines or ridges of the scapulae. 

 The processes for the attachment of the muscles also increase, as do the 

 vertebral or osseous portions of the ribs. The teeth also change greatly 

 in size and form after maturity is attained. They not only increase in size, 

 especially the canines, but become much worn and misshapen by long use. 

 In old specimens a greater or less proportion of the teeth are said to be either 

 entirely wanting or broken, as is the case in the older of the two specimens 

 before me.* Respecting the younger stages I am without data, as well as 

 in respect to sexual variation. In these points the present species dot's 

 not probably differ much from Callorhinus ursinus, adult females and the 

 young of which are described further on. It is well known, however, that 

 the females are much smaller than the males ; as already suggested, they 

 doubtless" also lack the greatly developed sagittal and occipital crests of 

 the males, as do the females of C. ursinus and Otaria jubata. 



Individual Variation. — The present specimens, though only two in 

 number and of different ages, indicate that the species under consideration 

 is subject to a great amount of individual variation. This variation is strik- 

 ingly shown in the skull, as seen in tin' following woodcuts (pp. 57-58). 

 After allowing for the differences age would make, as in the smaller size of 

 the sagittal crest, the rounded outline of the front edges of the inter- 

 maxillaries, the smaller size of the postorbital processes, the greater dis- 

 tinctness of the sutures, and perhaps the more sloping outline of the fore- 



* See Eig. 3, Plate I. 



