1 6 Journal of Comparative Neurology. 



named fissure which superficially seems to run into the Sylvian 

 at its base. This vertical fissure Spitzka has taken for the Syl- 

 vian. He describes it as follows : "It is the enormous hyper- 

 trophy of this field (auditory cortical) which crowds the Syl- 

 vian into its unusual vertical, nay anticlinal position." The 

 blunt frontal end of the cerebrum is an additional reason for 

 making the above condition possible but this view leaves a well 

 marked fissure in the usual situation of the Sylvian unaccounted 

 for. This opinion is still more difficult to accept when we come 

 to "sound " the fissures (examine their depths). The vertical 

 and the true Sylvian fissures meet superficially at the latero-ven- 

 tral angle of the cerebrum and if the sides of the SyK'ian be sep- 

 arated, it will be seen that the vertical fissure instead of directly 

 joining the Sylvian becomes a submerged fissure, at this point 

 corresponding to the preopercular area of the human brain, 

 and crops out again on the ventral surface on the front or ceph- 

 alic wall of the mouth of the Sylvian. In reality the vertical is 

 an open surface fissure in its dorsal half and overlapped by the 

 cortex (supergyre) in its ventral half. This condition is found 

 on both sides. 



Tiedemann (Icones cerebri simiarum et quorundam mam- 

 malium rariorum, Hidelbergia, 1821), in a figure of the base 

 of the seal's brain shows the ventral outcropping of a fissure in 

 the cephalic wall at the base of the Sylvian which is none other 

 than the terminus of the vertical. The present specimen con- 

 firms this exactly. 



In the feline brain the fissure approximating most nearly 

 to this vertical fissure of the seal would, in my opinion, be the 

 anterior fissure ; for if the frontal region of the cat's brain 

 could be moulded by any process of growth to the relatively 

 fore-shortened condition of the seal's brain the parts would as- 

 sume very much the same relations. The fissiira postica of the 

 cat's brain does not seem to be represented in the seal. 



The super-Sylvian and the post-Sylvian are well marked. 

 The two are continuous with each other at the surface on both 

 sides ; but at their union two branches are given off on the left 

 hemicerebrum and one on the right hemicerebrum. The pres- 



