SEA-LIOSS, AND SEA-BEAKS. 5 



Tlie grindera of the three skulls of H. Richardsi agree in heing 

 larger, broader, and with more distinct and longer lobes to the crown 

 than in any of our specimens of G. vitidinus. 



The lower edge of the lower jaw in 14316 and 1431 a is rather 

 compressed, with a decided prominence under the 3rd and 4th 

 grinders, which is very different from the dilated edge of the lower 

 jaw of C. vlhilinus ; but in the more adult skull of 1431 c, from 

 Japan, the whole lower jaw is very much thicker and more solid ; 

 and though there is a ridge showing where the prominence is in the 

 younger skulls, the internal side of the jaw is somewhat thickened, 

 80 that the prominence is not so distinct as in the two other jaws. 



Mr. J. W. Clark, who has a skull and skeleton of this Seal from 

 San Prancisco (P. Z. S. 1873, p. 5.56), considers it "the same as 

 Phoca vitidina.'' He appears to have founded this opinion on one of 

 the characters assigned to the species, and not on a comparison of 

 the skulls. 



The adult skull is like that of C. vitidinus, has the temporal muscles 

 divided by a very naiTow ridge, but differs from it in the following 

 particulars : — 



In HaUcyon Kichardsi the space between the orbits is broad, with 

 a prominent ridge above, which gradually tapers to a short narrow 

 edge ; this ridge in the front part of the brain-case widens and gra- 

 dually diverges to the sides, leaving a narrow triangular space, 

 which is twice as long as broad at the hinder edge. 



In the skull of the adult Callocephaliis vitidinus the central ridge 

 is linear, gradually widening in front to the hinder part of the 

 septum between the orbits, and behind the middle of the brain-case 

 diverging off into two ridges, leaving a broad triangular space, which 

 is rather shorter than broad, at the hinder edge of the brain- case. 



The front margin of the hinder nostrils of the three specimens of 

 Halici/on is rounded and entire, and of all the specimens of C'allo- 

 cephalus is deeper, with an angular notch in the middle of the front 

 edge. 



The lower jaw of Ualicijon Richardsi is much shorter and more 

 laterally spread out than the lower jaw of Cidlocephalas vitidinus 

 of nearly the same size, and the hinder end of the lower jaw 

 oi Halicyon is very much longer than that of C(dlocephalns vituliinis. 



The skin of Halicyon Richardsi is unknown, and has not been 

 compared with that of the Common Seal of Europe; and though the 

 skulls have some similarity, still there may be a great difference in 

 the external appearance of the animals. Many animals with dif- 

 ferent external appearance have nearly allied skulls, and the con- 

 verse^that is, with similar external they have different osteological 

 characters. 



*' Skull eloni/ate ; crown of adult Jtat, hroadhj triaiifinlar from between 

 the orhits. 



3. P,A_(iOMYS, Gray, Cat. Seals 4' Whales, p. 22 ; Siip/d. p. 2. 



Crown of the adult skull broad, triimgular, narrow between the 



