258 PHYSIOLOGICAL SERIES. 



casual glance the anterior ectosylvian sulcus i* nl.scnt, and 

 this at once reminds us of the spurious or apparent 

 lengthening of the "Sylvian fissure " in the Lion (rid, 

 supra) f where the anterior ectosylvian sulcus becomes 

 engulfed in the " Sylvian " (fig. 118). If the prominent 

 opercula-like lips of the "Sylvian fissure" in the Hy:i'na 

 be separated it will be found that the upper half of the 

 *' fissure" is really a submerged ectosylvian; in ><>iin 

 cases (vide fig. 131), but not in this, the lower extremity 

 of this ectosylvian element emerges from the " Sylvian '' 

 and deeply incises its anterior lip. But the condition 

 in the Hyasna's brain is very different even from that of 

 what we may call the anomalous Lion's brain (fig. 118). 

 There is a very large triangular submerged area (which 



Fig. 132. (Nat. size.) 



B. 



Holl would call "trigonum Sylvii ") overlapped not 

 only by a large anterior oporculum but also by a still 

 larger posterior operculum. This " trigone " is limited 

 both in front and behind by well-defined limiting sulci. 

 The inferior extremity of the posterior limiting sulcus 

 may emerge from the "Sylvian" cleft a short di-i 

 above the rhinal fissure (fig. 131, c, also specimen I ). 

 In the middle of the trigone there is a deep sulcus like 

 the feline "Sylvian fissure" (fig. 132, A). But a careful 

 -tudy of the condition:- exiting here clearly sho\v< that 

 neither the .-upcrlicial pattern formed by the niccti' 

 the opercular lips nor this MI! .merged >ulcus can he 

 regarded as strictly homologous to the "feline Sylvian 

 fissure." The whole arrangement is a more or less direct 

 mechanical adaptation of the growing cortex in this re 

 of kinking, and varies in different families of the ( 'arnivora 



