14 PROF. A. H. GAEEOD ON THE BEAIN 



one upward branch of the splenial fissure wliich _;'o/«s the fissura coronalis, and is not a 

 continuation of it, as in Sus. If it were not for this the fissura coronalis and fissura 

 lateralis would be continuous in Dicotyles. 



In Sus there is a minor longitudinal fissure between the fissura splenialis and the 

 fissura lateralis, or there may be two. In Dicotyles it is the same, the outer moiety 

 being the broader. 



The convolution between the fissura lateralis and the fissura suprasylvia is broader 

 than that between the fissura lateralis and the middle line — considerably in <S'«s, not so 

 much so in Dicotyles. Gyri of the included convolution, towards its outer border, make 

 its outer contour less distinctly marked than is its inner boundary, and the complication 

 may be increased by the presence of transverse bridging convolutions. 



In Dicotyles the superior limb of the suprasylvian fissure terminates, as in the Swine 

 and Cavicornia, without communicating with any other of importance, at the same time 

 that a wedge-shaped convolution is always more or less developed in the region under 

 consideration, with its backward-directed apex formed by the junction of the superior 

 and anterior limbs of the suprasylvian fissure. In the Cervidce it is the rule that the 

 superior limb of the above-named fissure blends with the posterior extremity of the 

 coronal fissure. The specimen of Elaphodus michianus figured by me ^ does not, however, 

 quite conform with this law. 



The adult Hippojiotamus brain which forms the subject of this communication differs 

 so much in the arrangement of the convolutions of the two sides, that from a study of 

 one or the other singly very diflPerent results might be arrived at. This evidently 

 depends upon the considerable development on the right side of bridging convolutions, 

 the great number of which in the brain of the Hippopotamus is laid special strain on 

 by Gratiolet-, who, whilst referring to the "middle series" of convolutions, remarks: — 

 " II acquiert une importance exceptionelle, et si son existence est au premier abord 

 dissimulee, cela tient a la grande quantite de plis de passages verticaux qui lient cet 

 etage superieur a I'etage inferieur proprement dit." On the left side these bridging 

 convolutions do not exist, and as a result an extra longitudinal fissure is seen, which 

 must be one of the typical sulci of the cerebral hemisphere, it being conspicuous in the 

 brain of Ilipjwpotamus liberiensis, according to Prof Macalister's outline sketch, though 

 absent in the figures accompanying Gratiolet's memoir on H. amphibius. 



The brain of the Hippopotamus is not richly convoluted. It is about as much 

 so as that of the genus Bos, decidedly less so than Camelopardalis giraffa or the 

 Camelidse. The considerably smaller Rhinoceros, Ceratorhiims sumatrensis^, has more 

 convolutions. 



Its weight immediately after removal from the skull was one pound and seven ounces. 



The most conspicuous fissure on the superior surface of the brain is one running from 



' P. Z. S. 1876, p. 757. ^ Anatomie dc I'Hippopotamo, p. 325. 



' Trans. Zool. Soo. vol, s. pi, Ixx. p. 411. 



