144 PROCEEDINGS OF THE ACADEMY OF [1881. 



differs from that figured by Garrod.' In the brains of the Llama 

 and Giraffe these secondary longitudinal fissures are often found 

 both anteriorly' and posteriorly, and are almost continuous with 

 each other ; on the other hand, in the brain of the Peccary used 

 by me for comparison, the secondar}- longitudinal fissure, usually 

 found posteriorly, is absent. The sylvian fissure in my Hippo- 

 potamus is quite evident, and within it I noticed a rudimentary 

 island of Reil. This fissure on the right side differs from that de- 

 scribed by Garrod, in that it is quite distinct from the Rhinal 

 fissure, there is, however, posteriorly a little connecting branch 

 between the two. I identified, as Garrod,^ on the left side of the 

 brain the supra-sylvian fissure with its branches, but these were 

 not well matched on the right side. On the mesial surface the 

 calloso marginal sent up a fissure which nearly reached the latiro 

 coronal and terminated in the genial. 



As is usuall}' the case in the artiodactyle, there was a secondary 

 fissure between the corpus callosum and the calloso marginal. 

 The minor convolutions of the brain of the Hippopotamus are not 

 very numerous. Indeed, the brain is much less convulated than 

 those of the Giraffe, Llama, or even the Peccary, used by me for 

 comparison ; in the general form of its hemispheres the brain of 

 the Hippopotamus resembled that of the Giraffe ; the cerebellum, 

 however, differed from that of the Giraffe, Peccary, and other 

 artiodactyles in that its largest diameter was transverse, whereas, 

 in the animals just mentioned, the largest diameter of the cere- 

 bellum was antero posterior ; the latter, however, seems to be the 

 case in the young Hippopotamus, at least judging from Gratio- 

 let's 3 figure. In the adult the cerebellum resembled more that of 

 the Manatee than that of the Artiodactyle. As the desoiption 

 and figures of the brain of the Hippopotamus given by Gratiolet ^ 

 and Garrod * are limited to the surface, it appeared to me ver}' 

 desirable that the interior of the ventricle should be exposed and 

 figured. On making the section, I found a septum lucidum. The 

 lateral ventricle was very large, recalling to my mind that of the 

 Manatee, dissected by me some years since. According to Macal- 

 ester's figure the ventricle is also large in Choeropsis. The general 



1 Op. cit., Plate III, fig. 1. ^ Qp. cit., Plate IV, fig. 3. 



3 Op. cit., fig. 2, PI. XII. * Op. cit.,. p, 317, PI. XII. 



5 Op. cit., p. U, figs. 1, 2, PI. 3; figs. 1, 2, 3, PI. 4. 



