URAIN OF THE ZEUGLODONXID^. 



629 



^culus is hypertrophied, but so, too, is the lobus medius and, in 

 addition, the latter is markedly asyrnmetrioal. 



These facts are readily appreciated from the figures. The 

 lateral aspect is instructive as revealing the relative size of the 

 cerebrum and the cer-ebellum. Couising over tlie latter from the 

 top to lateral angle is a ridge, probably indicating the site of a 

 venous cliannel, which converges upon the jugular leash posterior 

 to the acoustic nerve. 



From the posterior aspect we are impressed with the vertical 

 ^'lie" of the paraflocculi and their size relative to the lobus 

 medius. The massive "jugular leash" undoubtedly accommo- 

 dates the venous channels and the posterior cerebral nerves. 

 The dimensions of the medulla oblongata should be noted for 

 comparison with the later forms to be described. 



Text-figure 11. 



Intertubercular sulcus. 



Gasserian 

 ■ ganglion. 



Tuber cinereum. 



Psrafhcculus. 



■Ju^u/sr /essh. 

 Afedu//s ob/onffots. 



Ventral view of endocrauial cast of Proseucflodon atrox Andrews. 

 About i nat. size. 



M. 9265. 



The ventral view of Prozeuglodon atrox should be compared 

 Avith text-fig. 3. It will then be recognised that the structures 

 -on the basal surfade of Prozeuglodon atrox are entirely comparable 

 with those found on the basal surface of Zeuglodon sensitivus. 

 It is typically Zeuglodont in character — a fact which we will find 

 to be of great significance in comparing these endoci-anial casts 

 with that of Prosqualodon. No features call for special attention 

 at this stage of the discussion other than those noted in the 

 figures themselves. 



4. h. Zeuglodon intermedius, sp. nov. (M. 10173.) 



Zeuglodon hitermedius from the middle beds of the Middle 

 Eocene shows from the lateral aspect features comparable in 



41* 



