THE BRAIN OF THE ZEUGLODONTID^. 615 



33. The Brain of tbe Zefiglodohfidse (Cetacea). By Hay- 

 MOND A. Dart, M.Sc, M.B., Ch.M,, Professor o£ 

 Anatomy, University oE the Witwatersrand, Johannes- 

 buro; ; with a Note on the Skulls from which 

 the Endocranial Casts were taken. By 0. W. 

 Andrkws, D.Sc, F.11.S-, F.Z.S., British Museum 

 of Natural History. 



[Received May 18, 1923 : Roacf June 12, 1923.] 



* (Text-figures 1-24.) 



Table of Costbnts. 



Page 



1. Introduction 6l5 



'2. Material '. 6l6 



3. The two Kndocranial Casts unaccompanied by Osseoiis 



Remains 6l8 



a. Zeufflodon gcnsitivtis, sp, nov. (M. 12123.) 

 h. Zeiicfloddn elUotsmithii, sp. nov. (M. 12065.) 



4. The three Eridocranial Casts forming a Phyletic Series ... 627 



a. Frozenqlodon atrox Andrews. (M. 9265.) 

 h, Zeuglodon intermedins, sp'. nov. (M. 10173.) 

 c. Zeufflodon osiris Dames. (M. 10228.) 

 &. TaWe of Measurements of the Endocranial Casts 634 



6. The Zoological Position of the ZeuglodontidiB 635 



7. Comparison of Zcuglodont and Prosqualodont Bmins 638 



8. Tlio Trigeminus and the Law of Infiltration in Cerebellar 



Evolution 643 



9. Note on the Skulls from which the Endocranial Casts 



were talwu, by C. W. Andre ws, Di'.Sc, F.R.S. 648 



10. Bibliography OoS. 



1. Intuoduction. 



"The Cetacea rtr© connected with the marine Cn'l'nivor<^s 

 through tlie genus Zeuglodon, as Huxley has shown, and the points 

 of resemblance are so marked that the affinity cannot be doubted'' 

 (O. 0. Marsh, 1877). 



It has been suggested, in the past, tha,t these water-living 

 forms, which preserve in their skeletal parts characteristics 

 linking them with the ancestors of modern Oarnivora, were the 

 actual ancestors of the whales and the dolphius, i. e., the 

 Cetacea. The Zeuglodonts were therefore grouped together as 

 the Archseoceti. This sugge.?tion of a Carnivore (or Oreodont) 

 ancestry seems to have been universally admitted until Matthew 

 and G-regory (1910) pointed out various characteristics which 



