1922] Kellogg: Pinnipeds from Miocene and Pleistocene Deposits 83 



while, the young of Phocn groenlandica 1 ''' 3 do not enter the water 

 until their woolly coat is shed. This moulting usually takes from 

 fourteen to twenty days. It is nearly a month before the young of 

 Halichoerus grypus enter the water, according to the observations of 

 Hallgrimsson. 104 Very little seems to be known concerning the length 

 of time that elapses before the young of Monachus enter the water. 

 Dr. Racovitza 1135 has furnished the most complete observations regard- 

 ing this point on Lobodon carcinophaga. From his observations it 

 seems that the young enter the water in about three days, though the 

 young of Leptonychotcs weddelli, 166 a form in many respects the most 

 specialized, wait until they are nearly a month old. The young of 

 Mirounga leonina apparently require the longest time of all the 

 phocids, for Lydekker 1117 claims that it is more than two months before 

 they enter the water. 



The time that elapses before the young of the various forms enter 

 the water seems to be dependent upon the time required to moult the 

 natal pelage. When that has been accomplished the young assume 

 their pelagic life. However, this does not necessarily mean that the, 

 particular type which may happen to enter the water first, is the most 

 specialized. On the contrary, the young of many of the most special- 

 ized terrestrial mammals are helpless for a considerable period after 

 birth. It merely supplies the information that the cycle of moulting 

 advances further in utero in some forms than in others. 



The variations in the number of accessory cusps on the teeth of 

 Phoca vitidina have been studied and excellent figures prepared by 

 Allen. 1118 In this species the first upper and lower molars are alone 

 retained. However, Nehring 1 ' 19 has, in his account of the variations 

 in the skull of Halichoerus grypus that are brought about by age, 

 pointed out that the number of roots and cusps of the premolars may 

 vary considerably, and, what is more interesting, the second upper 

 molar frequently persists. 



ic3 Brown, R., Notes on the history and geographical relations of the Pinni- 

 pedia frequenting the Spitzbergen and Greenland Seas. Proe. Zool. Soe. London, 

 p. 419. 1868. 



is* Hallgrimsson, J., Bemaerkninger om den islandske Utselur. Kr0yer's 

 Naturh. Tidsskrift, vol. 2, p. 91. 1838-39. 



le s Racovitza, E. G., La vie des animaux et des plantes dans 1 'Antarctique, 

 p. 29. 1900. 



166 Wilson, E. A., National Antarctic Expedition, 1901-1904, Mammalia. Publ. 

 Brit. Mus., vol. 2, p. 57. London, 1907. 



167 Lydekker, R., The Royal Natural History, p. 147. London, 1894. 



188 Allen, J. A., The hair seals (Family Phocidae) of the North Pacific Ocean 

 and the Bering Sea. Bull. Am. Mus. Nat." Hist., vol. 16, pp. 467-470. New York, 

 1902. 



i<m Nehring, A., Sitz. Gesellsch. naturf. Freunde, pp. 107-126. Berlin, 1883. 



