78 Journal of Comparative Neurology. 



as the coronal. In TticJiccus (walrus) he figures as the presyl- 

 vian an apparent continuation of the lateral, and represents as 

 the coronal an apparent continuation of a third arched fissure 

 designated by him as the medilateral. 



The superorbital fissure in carnivora generally is designated 

 as the presylvian by many writers. 



The cruciate fissure is shown by Krueg, in Phoca, as exist- 

 ing only on the mesal aspect, occuppying the position of the 

 presplenial, or anterior sublimica of Kiikenthal. Leuret et 

 Gratiolet represent the fissure as seen on the ventral aspect at 

 the cephalic end. Other writers place it as usually seen in car- 

 nivora at the cephalic end of the dorsal aspect where it may or 

 may not reach the mesal surface. 



THE LATERAL VENTRICLE (PARACOELE.) 



On removing the dorsal portion of the hemicerebrum just 

 dorsal to the callosum the lateral ventricle is revealed. In the 

 bear the cavity bends cephalo-ventrad to form the precornu and 

 caudo-latero-ventrad to form the medicornu. The striatum is a 

 well defined body forming a portion of the floor of the ventricle 

 in the cephalic region. Parallel with the oblique margin of the 

 striatum is the fimbrial margin of the hippocamp. Between 

 these two margins — the rima (great transverse fissure) the chor- 

 oid (para) plexus — a continuation of the velum enters the floor 

 of the cavity. The hippocamp pursues its usual curved direc- 

 tion in the medicornu. 



In Phoca the lateral ventricle is relatively very much larger 

 than in the bear and the parts present quite different relations 

 to each other. The striatum is the same as in the bear ; along 

 its margin is a well developed plexus, but between this and the 

 fimbrial edge of the hippocamp there is an area equally as large 

 as the striatum ; this is the optic thalamus, but that portion of 

 of it represented in the floor of the cavity presents the same 

 general appearance as to its surface (endymal) as do the other 

 parts. The supposed delicate endymal membrane extending 

 from the plexus to the fimbria has been designated as the para- 

 tela by Wilder. The hippocamp, then, is removed some little 



