BRAIN OF CALIFORNIA SEA LION. 31 



The snperorhital, unlike Plioca and Callorhinus, lias a very distinct connection with 

 the ihinal fissure at about half of the distance from the Sylvian ilssure to the olfac- 

 tory bulb. It curves cephalo-dorsad with its convexity pointing cephalad. 



The cruciate fissure is more highly developed than in either of the seals. It 

 appears slightly upon the mesal aspect and on the dorsal surface extends obliquely 

 cephalo-laterad. Around its free end the coronal fissure demarcates a well-formed 

 sigmoid gyre. The appearances found in Fhoca approximate the conditions regarding 

 the gyre more than in Callorhinvs. 



Between the cruciate and ausate lies the postcruciate fissure. On the left hemi- 

 cerebrum it is well marked; on the right it is smaller and suijcrficially connected with 

 a minor fissure. 



On the right hemicerebrum a branch is given oft' from the cruciate extending 

 cephalo-mesad. It is the precruciate fissure. On the left hemicerebrum it is an inde- 

 pendent fissure. In neither case does it reach the mesal surface. The precruciate 

 with the cruciate forms a well-defined triangular area — the " ursine lozenge" of Mivart. 

 On the dorsal surface between the lateral fissure and the intercerebral cleft it is well 

 marked, but is not as deep as the other flssiires. It is the conflnis. On the right 

 hemicerebrum a short fissure connects it with the lateral. 



The medilateral Jissure arises at the caudal end of the cerebrum near the mesal 

 margin, in much the same i)osition as in Callorhinus, and continues down the ventral 

 aspect close to the caudal margin. 



MESAL ASPECT. 



The splenial fissure does not reach the dorsal margin as in the case of Phoca and 

 as on one side in Callorhinus. Its cephalic end is also nearer the caudal end of the 

 cerebrum than in either of the other two forms. In this respect the fissure occupies 

 an intermediate position in Phoca. It arches around the splenium of the callosum and 

 courses along the tentorial surface of the cerebrum as far as the caudo-lateral margin, 

 ending eight millimeters from the free end of the postsupersylvian. Two or three 

 short branches are given off along its course. Beyond the presence of a slight spur, 

 there is no evidence of a postspleuial fissure, nor of a supersplenial or marginal, as in 

 the case of the seals. A well- developed presplenial or flssura sublimica anterior ot 

 Kiikenthal is present, resembling that of P/ioat more than Callorhinus. No distinct 

 flssura sublimica was present, except in the case of the Thibet bear, where a small 

 minor fissure held the proper position. 



The genual and rostral fissures were present, and occupied the same general 

 relations to the cephalic end of the callosum as in Callorhinus. The callosal and 

 hippocampal fissicres have the same general relations as in other forms. 



ZALOPHUS CALIFORNIANUS, 



Through the kind permission of Professor Wilder I was permitted to remove the 

 brain from this young sea lion. Its mother came originally from the Pacific coast, and 

 the i^resent specimen was found dead in the cage with her while in transit to the East, 

 and was presumably not far from "term." It measured 43 centimeters long, and has 

 been in the Cornell Museum of Vertebrate Zoology for some years. 



The brain was in a fairly good state of preservation, and was i)hotographed soon 

 after its removal. It was too delicate to permit of much manipulation, and some of 



