ENDOCRANIAL ANATOMY OF OREODON 



303 



ramus lateralis suprasylvia (1. c). It may be present in varying 

 degree in any member of the ungulate group, and evidently 

 depends upon the expansion and consequent folding of the cortex 

 adjacent to the suprasylvian sulcus and dorsal to the anterior 

 ectosylvian operculum. The gyrus situated between the supra- 

 sylvian and lateral sulci is especially prominent in all the speci- 

 mens examined. 



Lb.S. 



S.iaK Pvoecf- R.V5. 



24 R'<* s. 



Figs. 23 and 24 Restoration of brain of Oreodon, right lateral and dorsa 

 views respectively. Abbreviations: S.cor.ans., corono-ansate complex; II, optic 

 nerve; V, trigenial nerve; VII, facial nerve, above which the two divisions of the 

 auditory nerve are indicated. Other abbreviations as before. 



Insular constellation. Ventral to the suprasylvian arch the 

 cortex is folded to form two opercula in a characteristic artio- 

 dactyl fashion. The true relations of these parts were only 

 verified after the preparation of the last specimen of the series 

 in which the opercula in question were not fully developed. In 

 all the other specimens the caudal operculum which forms the 

 enlarged caudal lip of the ramus posterior ectosylvii is as highly 

 developed as in Sus, and as a consequence the trigonum Sylvii 



