BHAIN OF THE ZliUaLODONTIB.E. 625 



3. h. Zeuglodon Ei.LioTSMiTJiii, sp. nov. (M. 12066.) 



Turning now to the lateral view of Zeuglodon elliotsmithii, 

 M. 12066 (text-iig. 5), and comparing it with Zeuglodon sensi- 

 tivus (text-fig. 1) we recognise in both the general Zenglodont 

 characters, which may be summarised as including a hyper- 

 trophied cerebellum tending to grow forwards over the cere- 

 abrum, hypertrophied trigeminal apparatus, and a diminutive 

 reptilian-like cerebrum bounded by tlie two former behind and 

 below, and an unusually well-marked sagittal sinus above and in 

 the mid-line. 



It will be noted that in Zeuglodon elliotsmithii the fore brnin 

 is very flnttened and slopes upwards and backwards evenly 

 towards the cerebellum, that the cerebellum is only slightly 

 elevated (1-10 mm.) above the flattened cerebrum, and that 

 appears almost vertical from the lateral aspect. In all these 

 features this brain contrasts strongly with that of Zeuglodon sensi- 

 tivus. Further, the trigeminal apparatus, although hypertrophic, 



Text-figure 5. 



Ssgttta/ sinus 



Ce'rebrs/ hem/sphere 



,Lobcjp mecfius' 

 cerede/U. 



O/factory pe</unc/e 



' \ (jasseri3n ^ 



Broken ma/ym of cast, ganghon. Midd/e cerebral i^esseJs. i 



Lateral view of endocranial cast of Zeuglodon elliotsniithi, sp. nov. M. 12060. 

 About i iiat. size. 



does not seem (juite so pronounced as in Zeuglodon sensiiivus, 

 although the fragmented nature of the cast, in this region, renders 

 a final statement upon this particular point impossible. 



The features to which reference has been made are to be recog- 

 nised from the dorsal aspect also. Note further from this aspect 

 that the lobus medius ceiebelli of Zeuglodon elliotsmithii is sym- 

 metrical, whereas the other is markedly asymmetrical (c/. text- 

 fig. 2), a point which is also clearly evidenced in the posterior 

 views (text-figs. 4 and 7). 



As these figures have been drawn to scale it is clear that many 

 features, such as the general flattening of Zeuglodon elliotsmiihii, 

 shown by the increased bi-parafloccular width, its general triangular 

 outline as seen from the dorsum, and its slender transversely- 

 elongated cerebellum mark the brain as characteristic and distinct 

 from that of Zeuglodon sensiiivus. These facts are brought out 

 by a comparison of the table of brain-measurements (vide infra). 

 Thus both the greater width and length of the. cerebral hemi- 

 spheres emphasize the flatness already leferred to, while both the 



