PROSENCEPHALON OF MAMMALS. 



117 



from the interhemispheral fissure outward and slightly forward. 

 The upper part of the hemisphere is thus here divided into tracts 

 which may be termed ( medial ' I, m, sylvian e, e f ,g, aud frontal ?z x . 

 In a small Plantigrade, the Coati (Nasuci), we find a longi- 

 tudinal fissure, fig. 88, 11, 11, which diverges outward as it 

 advances ; and a fissure, fig. 90, e, which is in advance of and 

 parallel with the sylvian, 5, but curves backward overarching 

 that fissure and subdivides the cerebral tract between the fissure, 5, 

 and the one marked n. Here, therefore, is a ground of choice, 



87 



88 



89 



Brain, upper view, 

 Stoat, Pidorias. 



Coati. Fox. 



Upper surface of right hemisphere. 



whether, viz., the fissures 8 or n in the Coati be the homoloo-ue 



' ~ 



of that marked 8 and n in the Stoat. The homology of 14 is 



90 



91 



92 



Coati. 



Cat. 

 Side view of brain. 



Fox. 



clearer, and the tract anterior thereto is more definitely or deeply 

 subdivided into a superfrontal fold ?z x , and a midfrontal one n" , 

 figs. 88, 89, Coati, Fox. 



In the Cat, figs. 83, 91, the longitudinal course of the fissures \\ 

 and 8 is more extensive ; the oblique fissure 12 crosses the anterior 

 end of 11, and marks out an anterior tract which is divided, trans- 

 versely, by 14. A fissure, 10, following the hinder contour of the 

 hemisphere, bends forward, between 11 and the interhemispheral 



