GENERAL OBSERVATIONS. 225 



have seen) behind the last molar of the normal series. They 

 are usually smaller than the normal molars, sometimes almost 

 rudimentary, usually without accessory cusps, and with a 

 smooth or nearly smooth cingulum. They are hence generally 

 recognizable by their size and form. In cases of suppression 

 it is usually the antepenultimate molar that is missing. This 

 molar also frequently falls late in life, but traces of an alveolus 

 in such cases usually attest its former presence. 



POSITION OF THE LAST UPPER PERMANENT MOLAR. 



In species with the sui^erior molars 5 5, the last (except in 

 Mumetopias) is placed opposite the posterior edge of the zygo- 

 matic process of the maxillary, varying slightly in position in 

 different individuals belonging to the same species, mainly, 

 however, in consequence of the thickening of the mastoid pro- 

 cess in old age. In species having the superior molars 6 C, 

 the last is usually* entirely behind the zygomatic x^i'ocess 

 of the maxillary, the fifth molar holding the same relative posi- 

 tion as in the flve-molared species. The exception presented 

 by Uumetopias seems at first view to favor the theory that the 

 last molar is homologically the sixth, and that the fifth is sup- 

 pressed, but in reality its position is posterior to that of the 

 last molar in the six-molared species, while the space between 

 it and the fourth is equal to or greater than that occupied 

 by two molars. 



GENERAL OBSERVATIONS. 



The largest species of the Otaries (genera Otaria and Eume- 

 topias) are Hair Seals, while the smallest (genera CallorMnus 

 and Arctoceplialus) are Fur Seals; but the species of Zalophus, 

 although Hah" Seals, are intermediate in size between the other 

 Hair Seals and the Fur Seals. All the Hair Seals have coarse, 

 hard, stiff hair, varying in length with age and season, and are 

 wholly without soft underfur. All the Fur Seals have an abund- 

 ant soft, silky underfur, giving to the skins of the females and 

 younger males great value as articles of commerce. The 

 longer, coarser overhair varies in length and abundance with 

 season and age. All the Hair Seals are yeUowish- or reddish- 

 bro'wn (in Zalophus sometimes brownish-black), generally dark- 

 est when young, and becoming lighter with age, and also in the 

 same individuals toward the moulting season. There is also 



* In Phocarctos both tlie fifth and sixth are behind the posterior edge of 

 the zygomatic process of the maxillary. 

 Misc. Pub. No. 12 15 



