74 Journal of Comparative Neurology. 



On the right hemicerebrum a branch is given off from the 

 cruciate extending cephalo-mesad. It is the precruciate fissure. 

 On the left hemicerebrum it is an independent fissure. In 

 neither case does it reach the mesal surface. The precruciate 

 with the cruciate forms a well-defined triangular area — the " ur- 

 sine lozenge " of Mivart. On the dorsal surface between the 

 lateral fissure and the intercerebral cleft there is a well marked 

 fissure but it is not as deep as the other fissures. It is the con- 

 finis. On the right hemicerebrum a short fissure connects it 

 with the lateral. 



The medilateral fissure arises at the caudal end of the ce- 

 rebrum near the mesal margin, in much the same position as in 

 Callorhimis and continues down the ventral aspect close to the 

 caudal margin. 



Mesal Aspect. The splenial fissure does not reach the dor- 

 sal margin as in the case of PJioca and as on one side in Callo- 

 rhimis. 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 the 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 post- 

 supersylvian. Two or three short branches are given off along 

 its course. Beyond the presence of a slight spur there is no 

 evidence of a postsplenial fissure, nor of a supersplenial or mar- 

 ginal as in the case of the seals. A well developed presplenial 

 or fissura sublimica of Kiikenthal is present, resembling that of 

 Phoca more than Callorhimis. No distinct fissura 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 relation to the cephalic end of the callosum as 

 in Callorhimis. The callosal and hippocampal fissures have the 

 same general relations as in other forms. 



