ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 



75 



r 



1cm 



cm 



0% 



Fig. 48. Dental alveoli in stained and cleared skulls (upper-ventral view) and mandibles 

 (lower-dorsal view) of 106-mm (left) and 132-mm (right) fetal walruses. (Photos by 

 K. L. Austerman) 



broader at the anterior than at the posterior end, such that the maxillary tooth 

 rows were strongly divergent anteriorly. The upper canines were about twice as 

 large as the premolars, with which they were aligned in the tooth row. In the 

 lower jaw, distinct diastemata were present between i3 and cj, as well as 

 between Cj and p2- No molars were evident, and none of the teeth had begun to 

 calcify. 



Fetus, 132 mm, 3 August (stained and cleared). — Primary follicle formula 



1-2-3 



1 



cyp 



1-2-3-4 



2 = 30. 



2-3 1^ 2-3-4 



The positions of most of the alveoli, as well as calcification centers in those of c^ 

 and p3 can be seen in Fig. 48 (right). The alignment of the maxillary tooth rows 

 was remarkably different from that in the previous specimen, due to broadening 

 of the palate posteriorly. The upper canine was already outside the incisor- 

 postcanine tooth row, in its characteristic position, lateral to pi . The follicle of pi 

 was smaller than those of the other premolars and no larger than it was in the 

 previous specimen. The diastemata between the lower canine and 13 and p2 

 remained distinct but narrower than in the previous specimen. 



