620 • PROF. R. A. BART ON TUB 



"Zeuglodon ist mindestens zu den hemiunosmatisclien Siiiige- 

 tliieren zu reclmen im Gegonsatze zu den anosmatischun Zahn- und 

 liiiTbenwaleu und ist audi durch normal verlaut'enden Nasen- 

 rachengiinge von letzteren unterschieden," says Stromer. In his 

 insistence on the retention of a sense of smell by these creatures, 

 he is justified even though his term *• hemianosmatic" seems 

 philologically meaningless. 



Along the dorsal border of the lateral aspect of the cast the 

 olfactory peduncle appears to merge into the sagittal sinus, which 

 is continued over the cerebrum towards the anterior border of 

 the cerebellum, where it dips into the " median tentorial depres- 

 sion " and receives veins from the cerebellar surface. 



Tlie cerebrum on either side is seen to be bounded by the 

 sagittal sinus above and by the cerebellum posteriorly (which 

 excludes all view of the mid-brain region from the dorsal or 

 lateral aspect). Ventrally there is to be seen anterior to the 

 region of the cerebellum designated "paraflocculus," a rounded 

 roll-like structure continuous anteriorly with the ophthalmic and 

 maxillary divisions of the trigeminal nerve. This bulging mnss 

 is a huge Gasserlan ycmglion which rivals the cerebral hemisphere 

 in "size, helps to mould the lateral contour of the brain-cose, and 

 gives rise to its three proportionately large trunks. Coursing 

 over the lateral aspect of the Gasserian ganglion (well illustratetl 

 in text-lig. 1) are the middle cerebral vessels. IJetween these 

 confines (sagittal sinus above, cerebellum behind, and G;isserian 

 ganglion below) in Zeuglodon sensiiivus the cerebrum bulges out, 

 displaying a perfectly smooth hemispherical surface with the 

 exception of the previously noted Sylvian depression. 



Behind the cerebrum lies the apparently irregular mass of the 

 cerebellum elevated to a height of approximately 15 mm. above 

 the cerebrum. From this it is separated by a tentorial sulcus, 

 which is of especial depth in the mid-line, forming a " median 

 tentorial depression." The most obtrusive feature of the cere- 

 bellum from the lateral aspect is unquestionably the lobus floccu- 

 laris (consisting of the flocculus and the paraflocculus). 



Elliot Smith has called this region the " paraflocculus" in his 

 description of the Zeuglodont brain, and this name is i-etained in 

 these figures. It seems that in most aquatic mammals the para- 

 flocculus is the portion of the lobus floccularis which undergoes 

 greatest expansion. The term paraflocculus may therefore be 

 regarded, for the purposes of this paper, as synonymous with 

 the lobus floccularis. 



Despite Bolk's association of the paraflocculus with tail-move- 

 ments, bears which have no tail (as Elliot Smith has pointed 

 out to me) liave, nevertheless, a well-marked paraflocculus. Ikit, 

 whereas the paraflocculus is present in most land-mammals, it 

 becomes especially hypertrophied in all marine Mammalia irre- 

 spective of the stock from which they have sprung. Thus 

 creatures so divergent as Otaria and Monachus (Carnivore), 

 Trichechus manatus (of Ungulate origin), and Phoaena (probably 



