44 



NORTH AMERICAN FAUNA 68 



Figure 21. — Fresh young adult dentition in the late juvenile or early subadult 

 stage of development. Note the rounded, blunt canines and spade-shaped 

 lower incisors which are used to scoop invertebrate organisms from their 

 shells. Found dead on the beach, 5 March 1962, Amchitka Island, Alaska, 

 weight 24 lb. (10.9 kg.), length 1,005 mm. (KWK 66-9-9) 



mals) then available. For this reason, the present description of 

 premature dentition differs somewhat from hers. 



In the following discussion, the terminology of Scheffer and 

 Kraus (1964, p. 296-298) is used. The ages at which individual 

 teeth erupt are approximations and are based primarily on body 

 size. A limited number of specimens was studied to determine the 

 progression of tooth eruption from birth to the adult dentition. 

 A detailed study of dental development remains to be undertaken. 



In a newborn sea otter (fig. 22), weight about 1.7 kg. (3.7 lb.), 

 the four canine teeth, two upper incisors and two lower first and 

 second pairs of postcanine teeth are erupted from the gums. At 

 birth there are a total of 26 deciduous teeth of which 10 are 

 visible (see formula). The fate of the fetal teeth that are erupted 

 from the bone at birth but are not gingivally erupted is not known, 

 but it appears that they are exfoliated without becoming func- 

 tional. 



