COMPARISON WITH ALLIED SPECIES. 611 



tlie same dimensions in exceptionally large old male skulls of P. 

 fcetida to be 186 mm. and 115 mm. The width at the mastoid 

 processes in the Baikal Seal, however, is only 100 mm.,* against 

 112 mm. in P.foetida. A very strongly marked difference is ob- 

 servable in the relative length of the facial portion of the skull 

 in the two species, this being very much narrower and longer 

 in the Baikal Seal than in the other, this, of course, involving 

 a corresponding narrowness of the nasal bones and the palatal 

 region. The vertical height of the skull is also much less than 

 in P. fcetida. Without going further into details, it may be suf- 

 ficient to state that the skull of the Baikal Seal is characterized 

 by great attenuation in every jiart, with great expansion of the 

 orbits. In dentition and in the general form of the palatal re- 

 gion there is a close agreement with the Kinged Seal, the Baikal 

 Seal being, in a word, a slender form of the Phoca fcetida type. 



It also diflers notably in coloration, being apparently never 

 spotted. According to Dr. Dybowski, the adults are silvery- 

 brown ("silberbriiunlich") above, and dingy silvery-brown 

 ("schmutzig silberbrjiun") below; in the younger animals the 

 silver-brown color has a whitish lustre ; in the newly-born young 

 the thick, long wool-hair is silvery- white. The length of the 

 full-grown animal is given as 1,300 mm. 



While it is pretty clear that the Caspian Seal and the Baikal 

 Seal are both specifically distinct from the Einged Seal, and 

 that neither of them has any near relationship to Phoca vituUna, 

 the points of difference between the two first-named are not so 

 evident. In coloration the Caspian Seal appears to not differ 

 greatly from the Ringed Seal; both consequently difl'er sim- 

 ilarly in color from the Baikal Seal, namely, in being spotted, 

 while the latter is con color. On the other hand, the Caspian 

 and Baikal Seals agree in being considerably larger than the 

 Ringed Seal, and in the skull being narrower in proportion to 

 its length, with the upper surface more convex. The Baikal 

 Seal, however, appears to be distinguished by the greater atten- 

 uation of the facial region coupled with a much greater expan- 

 sion of the zygomatic arches. 



The peculiar features of coloration presented by the Baikal 

 Seal have been given with uniformity since the time of Steller,! 

 who first made them known. Schreber's short description, 



* Estimated from Dybowski's figure. 



t Besclireibimg von dem Lande Kamtscliatka, 1774, p. 108. 



