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MR. A. H. GAEROD OX THE BRAIiSf OF THE SUMATRAN RHINOCEROS. 



Upper view of left cerebral 

 hemisphere of Ceralorhinus 

 sunuitrensis, showing general 

 direction of sulci. 



in the Equidte, as might have been surmised. The whole brain, however, is broader, 

 especially near the posterior portion of the cerebral hemispheres, where the breadth is 

 considerably greater than further forward. 



The accompanying diagram will facilitate the description. 

 It represents the disposition of the main convolutions upon 

 the superior aspect of one hemisphere, and exhibits the 

 direction of the sulci which divide them. Two diagonal sulci 

 cut up the posterior part of each lobe into three oblique 

 gyri, which may be called the (1) external, (2) middle, 

 and (3) internal gyrus. The middle and internal of these 

 fuse together near the transverse line which joins the two 

 rudimentary Sylvian fissures, anteriorly to which there is, 

 in the Equidae, no indication of further primary longitudinal 

 division. The external oblique gyrus continues, from this 

 liiie, directly forwards, and independent. 



In Ceratorhinus sumatrensis the internal oblique gyrus 

 is triangular in shape, its inner boundary being the great 

 longitudinal fissure of the hemispheres, into which it de- 

 scends a short distance. In the Equidse the inner boundary 



of this gyrus is more superficial, and can be seen as a straight longitudinal line, 

 just external to the fissure itself, in the superior view of the brain. The whole gyrus 

 is much broken up by minor foldings of its elements, especially in its median portion, 

 its outer moiety consisting of a minor gyrus, whose general direction is a continuous 

 oblique line, fairly regularly bent upon itself, first one way and then the reverse. 



The median oblique gyrus is divided into two nearly equal moieties by a fissure 

 running parallel to its direction, each half being much doubled upon itself. Anteriorly 

 bridging minor convolutions blend it with the internal oblique gyrus, about one third 

 distant from the anterior extremity of the hemisphere, in front of which the broad 

 oblong cerebral surface is divided by a longitudinal sulcus into two equal moieties, 

 both convoluted. In the great breadth and division of this anterior portion the 

 Ehinoceros under consideration difiers from the Equidse, and agrees with Rhinoceros 

 unicornis. 



The external oblique gyrus is much doubled on itself, and separated from the 

 Sylvian fissure, which it surrounds, by minor convolutions, more strongly differentiated 

 anteriorly. 



On the inner surface of the hemisphere the hippocampal gyrus is seen to be traversed 

 by minor sulci and slight folds which run parallel to its length, as in the Equids, the 

 calloso-marginal sulcus following the anterior bending of the corpus callosum, and 

 not, as in so many Artiodactyla (but not in the Equidse), becoming superficial 

 anteriorly. 



