10 THE FUK SEALS OF THE PRIBILOF ISLANDS. 



The condition of the last, or true molars is of value, particularly in the female, in 

 determining the age of a given animal, for while it can not be said how many years a 

 particular seal may have lived, yet it is possible to tell from the appearance of the 

 molars whether the animal is adult, middle aged, or old. (Seethe various figures onPl. I.) 

 As Dr. Allen has already noted,' irregularities in dentition are not infrequent in 

 the fur seal through the failure of one or more of the grinders to develop. A good 

 instance of this is shown in the skulls of two pups, a male and female, which were 



Jaws of male fur-seals, three, four, and oTer seven years ol age, three-fourths natural size. 



collected on the same day and in the same locality, and, curiously enough, possessed a 

 similarly abnormal dentition through the absence of the last molar in each side of 

 each jaw. 



Believers in the coalescence theory of the development of teeth may find a crumb 

 of comfort in the fact that in both cases the last tooth in the row was slightly wider 

 than usual, and a little more deeply grooved vertically. On the other hand, Mr. 

 Andrew Halkett^ has noted a case in which three upper molars were present. 



1 History of North Ajuericwi Finnipeds, p. 329, s MSS. report. 



