TTAND-LTST 



111' 



SEALS, MORSES, SKA-LTONS, 



AMI 



SKA-IUURS. 



Suborder PTNNIPE13TA, 



Oraif, Siippl. (^(it, Seah 4' Whales, p. I. 



The fur of several kinds of Seals changes so much in colour 

 during their life, and j>rescnt8 such diflierent appearances from youth 

 to adult, and even old, age, that it does not aftord a reliable cha- 

 racter for the distinction of the species. The best external characters 

 are the extent and nakedness of the muzzle, the smoothness or wavi- 

 ness of the whiskers, and the extent of hairincsKS betwiuiu the toes ; 

 but the most certain characters of the species are afforded by the 

 skulls and the form of the grindei-s ; and these characters an^ more 

 permanent tliaii the external ones. TIk; skull does not alter its 

 shape, except in the development of the scar and ridges for tlie 

 attachment of the temporal muscle ; and tlio perniaiu^nt teelh (which 

 are developed very soon after the birth of the animal) remain of the 

 same form during lif(\ 



The milk-teeth of the Seals and Sea-lions iV:c. are very small, 

 and are shed very eaily in life, indeed soon after birth, and replaced 

 by the i^ermanent series when the animals are a few weeks old. 

 The permanent teeth, when the crowns are first developed, are 

 more sharply marked than in the adult, for the edges of the lobes 

 or ridges become worn off as the animal increases in age. The teeth 

 become more separated from each other by the development of the 

 jaw-bones : in other respects they retain their characters throughout 

 life. 



1'he position of the teeth with regard to the bones of the skull 

 remains the same during the entire life of the animal ; they retain 

 the same place in the very young and in the adult skull ; and the 

 position of the grinders often affords a good means of dividing the 

 species into genera. For example, Mr. Allen, in his plates of 



IS 



