66 Journal of Comparative Neurology. 



sal surface of the brain. It is seen best from a dorsal view. It 

 arises at the margin of the intercerebral cleft. It arches in an 

 obliquely cephalo-lateral direction. From the cephalic extrem- 

 ity of the cruciate at a depth of fifteen millimeters there passes 

 off another fissure, which Krueg has represented as the precru- 

 ciate in certain carnivora, nearly to the mesal margin just dor- 

 sal to the olfactory bulb. The depth of these fissures at their 

 junction is from 12-15 millimeters. Between these fissures and 

 the intercerebral cleft there is a triangular shaped area to which 

 Mivart has applied the name of " ursine lozenge" (Turner), 

 thought by Mivart to be of considerable significance. Just 

 caudal to the cruciate fissure is a small fissure corresponding to 

 the postcruciate of Krueg. On the left hemicerebrum it is tri- 

 radiate, on the right it is straight. 



The Superorbital fissure has no connection with the rhinal. 

 Its length is 25 millimeters and its depth 8-10 millimeters. It 

 has a slight lateral convexity but has no branches. 



The Medilateral fissure. The name of this fissure is par- 

 ticularly appropriate in CallorJiinus ; not only is it on the mesal 

 side of the lateral fissure, but for a portion of its course is actually 

 on the mesal aspect of the brain. It curves around the caudal 

 margin of the hemicerebrum just on the verge of the cerebro- 

 cerebellar cleft. Between the lateral and medilateral fissures 

 there is a gyre averaging about 1 5 millimeters in width in which 

 there are two or three secondary fissures, which would seem to 

 indicate an attempt at the division of this gyre into two. 



Mesal Aspect. The callosal fissure presents no marked pe- 

 culiarity except upon the left hemicerebrum where, instead of 

 continuing around the genu of the callosum, it proceeds toward 

 the dorsal margin, or is continuous with a fissure coming from 

 this margin. On neither hemicerebrum is there any appear- 

 ance of a fissure immediately surrounding the genu. The hip- 

 pocampal fissure occupies its usual position, arching from the 

 splenium around the optic thalamus to the tip of the pyriform or 

 temporal lobe. 



The Splenial fissure. On the right hemicerebrum, this fis- 

 sure, if prolonged on the dorsal aspect, would be continuous 



