Fish, Brain of the Fur Seal. 6g 



the intervening Sylvian gyre. Both are relatively better de- 

 veloped than in CallorJiimis. The supersylvian has much the 

 same relation to the Sylvian as in Callorhimis. It is not distinct- 

 ly separated from the postsupersylvian although the interlocking 

 of some of the subgyral buttresses suggests the possibility of 

 an attempt at separation. On each hemicerebrum there is a 

 continuation of the postsupersylvian dorso-caudad beyond the 

 supersylvian. 



Fig. 3. Fig. 4. 



Fig. J. Cross section of a fissure, showing the obliquity of the walls. 



Fig. 4. A diagram to show the difference in the course of a fissure at its 

 surface and depth. The heavy lines represent the fissure walls at the surface. 

 The dotted lines and arrows represent the buttresses (b) formed by the bulging of 

 the deeper portion of the wall of the fissure. 



The frontal end of the supersylvian apparently forks, one 

 branch bending toward the Sylvian, the other continuing cephal- 

 ad. The ventral branch has a superficial union with the verti- 

 cal fissure which has been mistaken for the Sylvian. In my 

 former paper (1. c.) I designated this fissure as the anterior. 

 Krueg also had taken the same view. From the conditions al- 

 ready described in CallorJiinus, it seems to me that this fissure 

 is after all a disconnected portion of the supersylvian and that 

 presupersylvian would in some ways be a suitable name for it. 

 It is submerged in the cephalic wall of the Sylvian for the ventral 

 third of its course. In CallorJiinus the ventral two-thirds of the 

 corresponding fissure becomes submerged. 



The lateral fissure, as in the case of CallorJiimis, is the 

 longest fissure in the brain. In P/ioca, however, it is confined 

 entirely to the dorsal aspect of the cerebrum, and at its caudal 

 end it appears to terminate in a widely diverging fork or per- 

 haps a small transverse fissure, possibly corresponding to the 

 lunate (Wilder) of the cat. Its course is approximately paral- 

 lel with the intercerebral cleft and is somewhat tortuous. At 



