244 EUMETOPIAS STELLERI STELLER's SEA LION. 



The above table gives the principal measurements of the bones 

 of the skeleton. Measurements of two specimens are given, as 

 in previous tables, for the purpose of illustrating the variations 

 that occur in the relative size of different parts after maturity 

 is attained, and also for the purpose of illustrating individual 

 variation, which in some particulars these specimens exhibit 

 in a marked degree. The ribs, it will be observed, differ but 

 slightly in total length in the two; not nearly so much as 

 would be expected from the much greater bulk of the body of 

 the older specimen. It will be noticed that the principal differ- 

 ences in the ribs consist in the relative length of the bony to 

 the cartilaginous portions, in the older the ossified portion be- 

 ing much longer and the cartilaginous much shorter than in the 

 younger. An irregularity will be also observed in respect to the 

 sternum, the younger specimen having a supernumerary car- 

 tilaginous segment between the eighth and ninth normal ones. 



SEXUAL, ADOLESCENT, AND INDIVIDUAL VARIATION. In 

 respect to external characters, my material, consisting merely of 

 three adult males, does not furnish many facts touching these 

 points. These specimens, however, differ considerably from 

 each other, not only in color, but in size and proportions. Some 

 of these differences are clearly due to age (one of the specimens 

 being much younger than the others), but others equally great 

 cannot be thus explained. 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 scapula. The tuberosities for the attachment of 

 muscles also increase in size, as do the vertebral or osseous por- 

 tions of the ribs, as shown by the measurements already given. 

 The teeth also change much in size and form after maturity is 

 attained, and in old age often become much worn and broken 

 by long use. The general form of the skull in the males differs 

 considerably in different individuals of the same age, and also 

 undergoes great modification with age.* As already stated, this 

 consists mainly in the development of the crests and processes 

 for the attachment of muscles, and in the size and form of the 

 teeth. 



Mr. Elliott states that the young, when first born, have a 

 weight of about twenty to twenty-five pounds, and a length of 



* See Bull. Mus. Comp. Zool., vol. ii, pp. 56-60. 



