GEOGRAPHICAL DISTRIBUTION. 289 



more posteriorly, being in the adult at the posterior end of the 

 temporal fossa 3 , arid in the young at the orbits. The breadth 

 of the skull just in front of the brain-box in very young skulls 

 (those taken a few days after birth) is 40 to 42 mm., in those 

 three or four mouths old, 38 mm. ; in adult females, usually 22 to 

 30 mm. ; in adult males, about 30 to 35 mm. The amount of con- 

 striction varies somewhat in adult skulls of the same sex, the 

 constriction increasing with the advance of age. There is a 

 corresponding contraction posteriorly of the palatal region. In 

 very young skulls, the palate is widest at the pterygoid ha- 

 mnli ; in those a few mouths old it is nearly straight, but later 

 in life becomes narrowed posteriorly, the contraction being- 

 greatest in aged specimens, in which the width at the pterygoid 

 hamuli is a third less than it is at the last molar. 



The crests of the skull do not begin to develop until the ani- 

 mal reaches adult size, and attain their highest development in 

 very old specimens. In a series of thirty skulls, ouly two have 

 the crests remarkably developed, these being the two old male 

 skulls described by me in 1870.* In ouly one of the skulls of 

 the series, aside from the two above mentioned, are the teeth 

 much worn. The two very old skulls show, by their large size 

 and rugose character, that the deposition of bony matter is 

 continued to a very late period in life. 



COMPARISON WITH ALLIED SPECIES. Zalophns californianus 

 is too distinct in cranial characters and dentition to require com- 

 parison with any of the Hair Seals of other genera, while its 

 pelage and color afford obvious points of difference from the 

 Fur Seals. As respects the conformation of the skull, it finds 

 its nearest allies in Arctoccphalus, from which, however, it is 

 readily distinguished by its more elongated muzzle and dental 

 formula. It appears to closely resemble its congener, Z. lobatus, 

 both in size and color. Having no specimens of that species 

 at command, I am unable to state the points of difference be- 

 tween the two. The descriptions and figures of Z. lobatus indi- 

 cate their close alliance. 



GEOGRAPHICAL DISTRIBUTION. The exact boundaries of 

 the habitat of Zalopltus californianus cannot at present be given. 

 The only specimens I have seen are from the coast of California 

 and its islands, from San Diego and San Xicolas Island north- 

 ward to the Bay of San Francisco. Captain Scammou (see 



*Bull. Mus. Comp. Zool., vol. ii, p. 69; see ineasiirements at p. 70. 

 Misc. Pub. No. 12 19 



