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



mens being twice as heavy as in others. An equally note- 

 worthy variation is seen in the number of cusps on the teeth 

 of the premolar-molar series. In the upper teeth pm 1 has usu- 

 ally two cusps, but sometimes three. The other teeth have 

 usually three cusps, but pm 2 and pm 3 have often only two, 

 the anterior cusp being wholly suppressed ; quite as often pm 2 

 or pm 3 , or both, have four cusps, through the development of 

 an anterior cusp and of two posterior cusps. Frequently the 

 corresponding teeth on the two sides of the jaw vary in the 

 number of cusps. While the difference is not sexual, extra 

 cusps appear to be more frequently developed in the male 

 than in the female. 



In the lower teeth pnij and the molar usually have three 

 cusps each, and pm 2 _ 4 have usually four each. The lower 

 molar is of special interest in comparison with the lower molar 

 in P. vitulina, P. richardii, and P. ochotensis, in which the 

 number of cusps varies from three to four. In Phoca hispida 

 in about 33 per cent of the skulls the molar has four cusps, 

 .and in the other 66 per cent only three cusps. In about 12 

 per cent the molar on one side of the jaw has three cusps and 

 on the opposite side four cusps. The difference is not sexual, 

 since males and females occur in both series. 



5. Phoca (Pusa) hispida gichigensis, subsp. nov. 

 OKHOTSK SEA RINGED SEAL. 



Type, No. 18276, ? , young adult, Gichiga, Okhotsk Sea, Oct. 12, 1900; 

 N. G. Buxton, Jesup North Pacific Expedition. 



Similar to P. hispida, but very much smaller, and with relatively 

 weaker dentition. 



This subspecies is represented by two skins and their skulls, both young 

 females, taken at Gichiga, on the western coast of the Okhotsk Sea. One 

 of the skulls is complete; the other consists of only the lower jaw and 

 the rostral portion of the skull, including the complete dentition. 



The external measurements of one of the specimens (No. 18277) are as 

 follows: Total length, 770 mm.; tail, 90; hind foot, 190. The other 

 : specimen, of which apparently no measurements were taken, is some- 

 what larger. 



The type skull measures as follows: Basal length, 139 mm.; greatest 

 .zygomatic breadth, 86; mastoid breadth, 92; front edge of intermaxillae 

 to pterygoid hamuli, 75; front border of incisors to posterior border of 



