Fish, Brain of the Fur Seal. 65 



it until it fully reaches the dorsal surface, then approaching to 

 within eight or nine millimeters of the intercerebral cleft, it con- 

 tinues its arched course in a cephalo-ventral direction approach- 

 ing to within five millimeters of the presupersylvian fissure at 

 about the level where the latter becomes submerged in the Syl- 

 vian. 



The lateral is a deep fissure and no distinct evidence of 

 shallows could be detected along its course although in certain 

 places the presence of submerged buttresses interfered to some 

 extent with the soundings, the average depth being from ten to 

 thirteen millimeters. The cephalic extremity of the fissure ter- 

 minates in a fork, more marked on the left hemicerebrum than 

 on the right. Does this widely forked termination represent 

 the ansate fissure ? It has the same appearance and relation to 

 the lateral as seen in the cat, and provisionally, it is here so 

 designated. 



The gyre, bounded by the lateral and supersylvian fissures 

 and its parts, is indented by numerous branches originating 

 from the above named fissures. There are also occasionally in- 

 dependent minor fissures present in this gyre. 



The Ectolateral fissure. The ectolateral on the right 

 hemicerebrum is a distinct fissure. It begins on the ventral 

 surface near the termination of the postrhinal ; it then proceeds 

 dorso-caudally, parallel with the postsupersylvian and for about 

 the same distance. On the left side it is a shorter fissure and 

 superficially is continuous with the dorsal portion of the postsu- 

 persylvian but a shallow separates a deeper connection. On 

 the left side side of the adult Callorhinus, a somewhat similar 

 condition exists except that the superficial union of the ectolat- 

 eral is with the ventral portion of the postsupersylvian. 



The Coronal fissure is about three centimeters in length and 

 extends except for a slight caudal convexity in an almost verti- 

 cal (dorso-caudal) direction. Its greatest depth is eight milli- 

 meters. On the right hemicerebrum it gives off a slight spur 

 pointing toward the Sylvian. In Callorhinus it represents, per- 

 haps, the least complicated fissure in the brain. 



The Cruciate fissure is not at all represented upon the me- 



