88 Journal of Comparative Neurology. 



in Callorhimis except upon the left hemicerebrum of the pup. 

 In Phoca the two fissures are distinctly separated 



The postsupersylvian is continuous with the supersylvian 

 in Ursus and Zaloplms but separated in Callorhimis. They are 

 apparently continuous in Phoca, but a dorso-caudal branch and 

 the presence of submerged buttresses at this point of junction 

 would indicate that there was some attempt at separation. 



In the bear there is no elongation of the paracoele to form 

 a postcornu ; in the sea lion Murie finds a distinct postcornu 

 present ; in Callorhimis it is quite rudimentary ; in Phoca Tiede- 

 mann represents the paracoele with no appearance whatever of 

 a postcornu. My own specimen, which so far as I know is nor- 

 mal, shows a postcornu relatively as large or larger than in the 

 primate brain with a distinct calcar or hippocampus minor in 

 which a portion of the splenial appears as a total fissure. 



With the exception of the bear, concerning which I have 

 no 'data, and the additional brain from an adult Callorhimis and 

 Mo7iachtis all of my material was from specimens not more than 

 one year of age. It is believed, judging from a comparison of 

 the brain of the young with that of the adult Callorhimis as to 

 bulk and complexity of fissuration, that comparatively little or 

 no change occurs, especially in the latter respect. 



Mr. Lucas, who had casts of the cranial cavities prepared 

 from the male and female fur seal, finds but slight difference in 

 the size of the cavities, notwithstanding the fact that the bulk 

 of the body of the male is about four times as great as that of 

 the female. Of the representatives of the five groups examined, 

 the brain of Callorhimis shows a greater number of minor fissures 

 and a more intricate arrangement and branching of larger fis- 

 sures. With regard to the ground plan of the fundamental fis- 

 sures, and allowing for the difference in the shape of the brains, 

 that of the eared seals, Callorhimis and Zalophus, approximates 

 in general more closely to that of the ursine carnivora than does 

 Phoca. The latter, or earless seal, in some respects, appears 

 aberrant. The arrangement of the cruciate and postrhinal fis- 

 sures would seem to link it with the canine and feline carnivora ; 

 while the peculiar development of the occipital region and the 

 large development of the postcornu with its calcar point toward 

 primate conditions. The group of lemurs is also said to pos- 

 sess a postcornu and to have affinities with both the carnivora 

 and the primates. As a matter of convenience a table of the 

 more interesting regions in the representatives of the different 

 groups examined is herewith appended. 



