468 Bulletin American Museum of Natural History. [Vol. XVI, 



females. In addition to these are two skulls from the coast 

 of Maine, sexed as male and female, received for examination 

 from the U. S. National Museum, making 13 in all. This 

 material shows that the toothrow in the females is fully as 

 long as in the males, but that the individual teeth are very 

 much heavier in the males, so that while in the females the 

 teeth, except pm 2 and pm 3 , stand in a straight line one behind 

 the other, with little or no obliquity of insertion, in the males 

 the teeth are so much larger that there is not room for them 

 in a straight line, and the axis of insertion for two of the upper 

 and three of the lower teeth (pm 2 " 3 and pm 3 _ 4 ) is more or less 

 oblique to the axis of the jaw, the divergence in the two axes 

 amounting in some cases to fully 45. 



Male. In the male pm 1 is small and conical and generally 

 has a more or less oblique insertion at the postero-inner base 

 of the canine; pm 2 and pm 3 are much larger, subequal, and 

 inserted obliquely to the axis of the toothrow, the angle being 

 greater in pm 2 than in pm 3 , and varying in different individ- 

 uals ; in pm 4 and m 1 

 the axis of insertion 

 is usually parallel to 

 the axis of the tooth 

 row. 



The upper teeth, 

 except pm 1 , are usu- 

 ally tricuspid, pm 2 , 

 pm 3 , and pm 4 hav- 

 ing a main cusp 

 high, pointed, and 

 directed backward 

 and two accessory 

 cusps behind it, the 

 anterior cusp being 

 either wholly sup- 

 pressed or present as 



a rudiment. In pm 3 the posterior cusp is sometimes sup- 

 pressed or so rudimentary that the tooth is practically 

 bicuspid instead of tricuspid. The same exceptional con- 



$ . Am. Mus. 



Fig. i. Phoca vitutina, ' young adult 



No. 13969, probably from coast of Maine. Upper dentition, 

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



