NERVOUS SYSTEM. VERTEBRATA. 251 



of this sulcus, which has already been noted in the Cats, 

 Sloths, and other forms. 



According to Holl the representative of the Sylvian 

 fissure is found in a small notch above the bend in the 

 rhinal fissure. But there can be little doubt that this really 

 represents what Holl himself would call the " anterior ter- 

 minal sulcus of the trigonum Sylvii." It is continuous, 

 under the pallial operculum, with the orbital (presylvian) 

 sulcus. On the right hemisphere this notch is so insignifi- 

 cant that it might easily pass unnoticed (fig. 123, x). 



The sulcus which at a casual glance would be unquestion- 

 ably called " Sylvian fissure " in this hemisphere is fairly 

 deep and extensive, and opens freely into the rhinal 

 fissure behind the before-mentioned notch or " Sylvian 

 fissure" (according to Holl). Holl regards this sulcus us 

 the posterior ectosylvian : and there can be no doubt that 

 it does represent the posterior ectosylvian ; but it is some- 

 thing more a confluence of the latter and the sulcus 

 which Holl calls " posterior terminal/' In the case of an 

 anomalous Cat's brain (vide specimen D. 292) it was seen 

 that the ectosylvian sulcus and the " feline Sylvian fissure " 

 might be compensatory factors in relieving the tension of 

 pallial expansion in this region ; we know also that it is not 

 uncommon for the posterior ectosylvian sulcus to open into 

 the Sylvian fissure or to join H oil's " posterior terminal 

 sulcus " ; it is also known to be unusual for the ectosylvian 

 sulcus to join the rhinal fissure, whereas it is the usual 

 arrangement of the Sylvian fissure : these facts and, finally, 

 a comparison with other Viverridse and with Carnivores of 

 other families (see especially Holl's figures of the brain of 

 a Cheetah [Taf. xi. fig. 2] and of a Fox's brain [Taf. xi. 

 fig. 12]) show that this posterior sulcus (fig. 123) in the 

 Civet ought to be regarded as the representative not only 

 of the posterior ectosylvian sulcus, but also of the " feline 

 Sylvian " fissure *. 



* If we compare this brain with that of the Jaguar (D. 297)j we can 

 greatly simplify matters by calling the sulcus labelled " SYL. ECTOS. 

 COMP." (fig. 123) simply " pseudosylvian,*' and the sulcus x the repre- 

 sentative of that similarly labelled in figs. 116 and 117. 



