32 THE FUR SEALS OF THE PRIBILOF ISLANDS. 



the fissures were uot sounded as tliorougbly as in the other specimens. The cerebrum 

 of this specimen does not show the same degree of complexity relative to the flssura- 

 tiou as indicated byMurie' in Otarla jubata. A direct comparison of the fissures, 

 however, is not easy, as the latter author attempts to homologise them with those of 

 the human cerebrum. 



The olfactory apparatus is well developed. Not as largely as in the bear, however, 

 but greater than in either of the seals. The rhinal fissure, as in the other forms, is 

 well marked, and passes caudad into the mouth of the Sylvian fissure. The post- 

 rhinal is formed from the subtissure (postica?) and has no connection whatever with 

 either the rhinal or Sylvian. 



LATEIiAl, ASPECT. 



The Sylvian is prominent and occupies its usual position. In its caudal wall is a 

 subfissure (postica?) and subgyre, which, as in Callorhinus, is continuous on the 

 ventral aspect with the pyriform or temporal lobe. 



The siipcrsyh-iati, with its cephalic and caudal portions, the pre- and postsuper- 

 sylvian, is more nearly in accord with the conditions Ibund in the bear than in either 

 of the seals. It represents an intermediate condition between the two. The presuper- 

 sylvian li«s very close to the Sylvian, but does not actually enter it, as in the seals. 

 Its average distance from it is about 4 millimeters, while the distance from the Sylvian 

 to the postsui)ersylvian is four times as great, or 16 millimeters. There is no sign of 

 disconnection between either the supersylvian and the postsupersylvian, or the sui)er- 

 sylvian and the presupersylvian. The supersylvian Ibrks or sends out a branch 

 cephalad connecting with the ansate fissure exactly as in Pkoca. 



The lateral fissure is, relatively to the length of the cerebrum, shorter than in any 

 of the other forms. Its (lephalic end and its relation to the ansate iis again exactly the 

 same as in Phovn. ( )n the left hemicerebrum the lateral is disconnected at a little more 

 than half of its length by a narrow isthmus. 



The coronal fissure corresponds with that of Fhoca, connecting, superficially at 

 least, with the ansate, and thus, indirectly, with the cei)halic branch of the supersylvian 

 and the lateral. 



The ansate fissure, as has already b«en intimated, like that of I'lioea, is irregular 

 in its form and connects with the fissures above mentioned. 



The ertol((tcral fissure is quite well down toward the ventral portion of the cere- 

 brum and, as in Callorhinus, appears upon the ventral aspect. 



The medilateral fissure is scarcely perceptible on the lateral aspect; it lies exactly 

 along the caudal margin of the hemicerebrum, as in Callorhinus, and is better seen in 

 a mesal view. 



The cruciate accords, in position and relation, more closely with the conditions 

 found in the bear and Callorhinus; but while it reaches to the mesal surfiice of the 

 hemicerebrum it does not cut it as far as in the bear and Fhoca. 



The precruciate and the postcruciate fissures are likewise present and have exactly 

 the same relations as in the bear and Callorhinus. 



MESAL ASPECT. 



The callosal fissure is well developed. On the right hemicerebrum it does not 

 continue around the genu, as in the left. 



' 1874, Trausactious of the Zooloj^ical Society of Loudon. 



