ENDOCRANIAL ANATOMY OF OREODON 311 



CONCLUSION 



As a result of the endocranial data thus accumulated it becomes 

 evident first that Oreodon presents certain primitive and gener- 

 alized characters which may be summarized as follows: A, prim- 

 itive characters: small volume of its cerebrum in comparison with 

 allied modern forms of similar bodily dimensions ; limited caudal 

 expansion of the neopallium as evidenced by the exposed dorsum 

 cerebelli; practical absence of presylvian neopallial area; appar- 

 ently uninterrupted intracranial course of the internal carotid 

 artery (absence of rete mirabile). B, characters of rhinenceph- 

 alon: large terminal olfactory bulbs and extensive lamina crib- 

 rosa; massive olfactory tractus and bulbus; macroscopic tractus 

 bulbo-tuberculare ; pyriform lobes well developed and very large 

 in proportion to the bulk of the cerebrum above the rhinal fis- 

 sure. C, artiodactyl characters: foramen lacerum anterius trans- 

 mitting ophthalmic and maxillary division of the trigeminus; 

 foramen ovale for mandibular division of trigeminus; long pro- 

 cessus acuminis ectosylvii at junction of rostral and caudal ecto- 

 sylvian opercula; pseudosylvian sulcus as in modern carnivores 

 and ungulates; lateral sulcus in no case communicating rostrally 

 with corono-ansate; presence of small ramus lateralis suprasylvii 

 of Holl; insular cortex defined by anterior and posterior ecto- 

 sylvian sulci, rhinal fissure and presylvian sulcus; sigmoid 

 curvature of lobulus medianus posterior of the cerebellum; loop 

 formation of formatio vermicularis cerebelli. In the first analy- 

 sis therefore it is evident that Oreodon was a primitive, macros- 

 matic artiodactyl.^ 



Oreodon presents, however, other and more determinate endo- 

 cranial characters which, while confirming its artiodactyl rank, 

 render its status within that order difficult to define. These 

 characters fall naturally into two categories as follows: A, rumi- 

 nant characters: junction of the corono-ansate complex with the 



' It is a fact of no small interest that most of the features of the cerebral fis- 

 sural pattern which are shared in common by modern perissodactyls and artio- 

 dactyls and whose presence in some form gives to the brain its so-called 

 'ungulate' character, are located in the caudo-Iateral convex surface of the 

 cerebrum (cf. 'ungulate' ectosylvian, suprasylvian and lateral sulcal config- 

 uration). 



