NERVOUS SYSTEM. VERTEBRATA. 239 



indents this submerged posterior lip and separates it from 

 the general surface of the hemisphere, so that a much more 

 definite submerged area is thus marked off. 



The long, deep orbital (or presylvian) sulcus is placed 

 far forward : it opens into the rhinal fissure, and it resembles 

 that of the Sloths. 



It is a characteristic -of the Cats to have two vertical 

 ectosylvian sulci anterior and posterior which do not 

 unite above to form an arc as they do in the Dogs : thus a 

 broad cortical bridge, which Meynert has called the "gyms 

 felinus" joins the first and second arcuate gyri of Leuret. 



There is a deep suprasylvian sulcus which is almost 

 horizontal ; it becomes continuous with the vertical post- 

 sylvian (or posterior suprasylvian) sulcus of Owen. 



The latter extends vertically downward to a point on the 

 caudal margin of the hemisphere at the junction of its 

 middle and lower thirds. 



The " lateral " sulcus pursues a sagittal course midway 

 between the suprasylvian sulcus and the mesial edge. In 

 front it bends outward parallel to the suprasylvian and 

 gives off an " ansate " branch. 



The " post-lateral " sulcus begins anteriorly opposite the 

 junction of the suprasylvian and postsylvian sulci, and 

 pursues an arcuate course parallel to the medio-caudal 

 "angle" of the hemisphere. On the right hemisphere it 

 is joined to the lateral, but is separate on the left side. 

 There is a large transverse crucial sulcus placed very far 

 forward on the anterior pole of the hemisphere, immediately 

 behind the mesial extremity o the orbital sulcus. It 

 crosses the mesial edge and proceeds horizontally back- 

 ward on the mesial surface for a short distance above the 

 genu o the corpus callosum. 



There is a short oblique coronal sulcus midway between 

 the ends of the suprasylvian and crucial sulci. Its upper 

 (posterior) end is opposite the angle between the lateral 

 and ansate sulci, and its lower (anterior) end is close to the 

 orbital. In front of the ventral extremity of the anterior 

 ectosylvian sulcus there is a short oblique " diagonal sulcus." 

 It is not uncommon to find the latter joined to the former 

 sulcus. In other cases the diagonal sulcus may be absent. 



