1902.] 



Allen, North Pacific Phocidce. 



469 



vitulina, 



g adult ' $ . Am. 



youn 



Mus? No. 13969, probably from coast of Maine. 

 Lower dentition, outside, inside, and crown views of 

 teeth. Nat. size. 



dition occurs less frequently in pm 2 . The molar is tricus- 

 pid, but in a different way, there being an accessory cusp 

 both before and behind the main cusp; the accessory cusps 

 are subequally developed, 

 but generally the pos- 

 terior is larger than the 

 anterior, which latter is 

 sometimes quite obsolete. 

 In the lower jaw the 

 teeth are much heavier 

 than in the upper jaw, 

 more serrated, more 

 crowded, and more given 

 to the development of 

 what may be termed ad- 

 ventitious cusps. Pm 2 . 4 

 normally considerably 



overlap each other and have a very oblique insertion, pm 2 

 and pm 3 being set rather more obliquely than pm 4 , the 

 molar alone usually having the axis of insertion parallel to 



the axis of the tooth- 

 row. The teeth are 

 usually 4-cusped, 

 but not infrequently 

 5-cusped, more rare- 

 ly 6-cusped, there 

 being a main, high- 

 pointed cusp, with 

 two well defined 

 cusps behind it and 

 one or two, and 

 sometimes three, in 

 front of it, the inner 



Fig. 3. Phcca vitulina, 

 No. 14442, probably from coast of Maine, 

 outside, inside, and crown views of teeth. Nat. size. 



young adult 

 M; 



Am. Mus. 

 Upper dentition, 



front border of the 



cingulum in heavy 



unworn teeth being often serrated with cusplets which in- 

 crease in size toward the main cusp. The molar has normally 

 four simple subequal cusps, the second or main one being the 



