ENDOCRANIAL ANATOMY OF OREODON 301 



and lateral olfactory tracts. From the latter, a series of fibers 

 arise which pass obliquely over the rostro-lateral margin of the 

 prominent olfactory tubercles and constitute the tractus bulbo- 

 tuberculare. 



Caudal of the tuberculum and between the optic chiasma and 

 the pyriform lobe lies the locus perforatus anticus about which 

 no further details can be given. At the rostro-mesial angle of 

 the ventral surface of the broad caudal expansion of the pyriform 

 lobe, a small circumscribed eminence is present in all the speci- 

 mens, evidently corresponding to the 'gyrus lunaris' of Retzius 

 which, as Elliot Smith (12) has shown, is realty the surface of 

 the nucleus amygdalae. The pyriform lobes are very large in pro- 

 portion to the size of the neopallium and on either side are sharply 

 demarcated therefrom by the well defined rhinal fissure. In 

 short it may be said that the rhinencephalon in Oreodon is devel- 

 oped in a manner characteristic of a highly macrosmatic mammal. 



Restoration of brain (figures 23 and 24) 



From the data gathered in the study of this series of casts it 

 is possible to arrive at a quite accurate estimate of the general 

 morphology of the brain of Oreodon. Since such information to 

 a large extent may be epitomised in the form of drawings, an 

 attempt has been made in this direction in figures 23 and 24. In 

 these restorations the details of brain stem configuration and 

 those of the exposed portion of the midbrain have been added 

 for the sake of completeness and are largely matters of surmise. 

 The details of cerebral and cerebellar morphology, on the other 

 hand, are based on observed facts and must closely approximate 

 the truth. 



Neopallim?! 



Sulcus lateralis. In all the specimens examined the lateral 

 sulcus is well marked and shows no tendency towards duplica- 

 tion, branching or other irregularity. The sulcus in question 

 forms a sharply cut groove parallel to the median border of the 

 hemisphere and separated therefrom by a broad slightly depressed 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 32, NO. 3 



