AND OTHER PARTS OF HIPPOPOTAMUS. 13 



posterior extremity ceases, whilst anteriorly it continues nearly as far forward as the 

 perpendicular level of the genu of the corpus callosum, which is partly embraced ante- 

 riorly, as it were, by a small Jissura gemudis (g). 



The outer aspect of the hemisphere has a basal fissure running nearly its whole length 



the Jissura rhinalis (rh), some little distance above which the anterior and posterior 



limbs of the sylvian fissure (sa and sp) diverge, the hinder extremity of the latter sending 

 downwards an extension to meet it. The anterior end of the anterior limb of the syl- 

 vian fissure also joins the posterior extremity of the small pisesylvian (ps) fissure, concave 

 upwards, situated low down in the outer frontal region, with another small and very 

 similar diagonal fissure (d) half way between it and the coronal fissure (co). The 

 fissura postica (p) is a small one between the hinder part of the fissura rhinalis and the 

 posterior limb of the supra-sylvian fissure. 



So much for the typical cerebral convolutions in the Ungulate animal, which undergo 

 special modifications in the different families of the order, some of which are particularly 

 constant, and must be here referred to in order that comparisons may be made between 

 the Hippopotamus and its allies. 



The brain of the genus Sks, together with Phacochcerus, is distinguishable from that 

 of any other Artiodactylate animal by one or two well-marked characters, the most 

 striking of which is the blending of the coronal with the splenial fissure by means of a 

 curved sulcus of so considerable a depth that the convolution between the middle line 

 of the hemisphere and the coronal fissure appears to be quite cut off from the rest of the 

 superior cerebral surface. The praesylvian fissure, however, as usual, runs up on the 

 inner side of the outward-directed anterior extremity of the coronal fissure. Behind the 

 sulcus of communication between the fissures just referred to there is always an equally 

 characteristic second one, parallel to it, and a short distance behind it, joining the fissura 

 splenialis and a prolongation of the superior limb of the suprasylvian fissure. Again, 

 as Dr. Kreug puts it, the posterior extremity of the suprasylvian fissure turns downwards 

 on the outer side of the hemisphere, and ceases near the lower border of the brain ; 

 whereas in the Cotylophora it runs backwards and iivwards rather than outwards. In 

 my opinion this arrangement is better indicated by saying that the descending limb of 

 the suprasylvian fissure is developed in the Swine at the expense of the posterior, whilst 

 in the Cotylophora the posterior limb is large and the descending limb rudimentary. In 

 the Swine, also, the fissura rhinalis and the fore-and-aft prolongations of the sylvian 

 fissure become continuous. In the Cotylophora they do not unite, the former being at 



a lower level. 



A careful comparison of the brain of Blcotyles taja^u with Dr. Kreug's illustration 

 of the same in IJ. torquatus does not lead me to see that Dkotyles resembles the true 

 Swine so closely as might be expected from that author's sketch. The characteristic 

 descending limb of the suprasylvian fissure is quite wanting in the two specimens at my 

 disposal, Tnd its posterior limb turns inwards slightly, as in the Cotylophora. There is 



