564 



Notes and Correspondence. 



[July, 



thecus, but not reaching to that of 

 the Gibbon. The folded convolution 

 /is not sharp, as in the Cercopitheci, 

 but is less elevated, and describes 

 a rounded curve ; its descending 

 branch is larger and thicker at its 

 root, which becomes developed, and 

 presents a feeble, but distinct 

 swelling. The fissure of Sylvius 

 and its marginal folds, in conse- 

 quence of this increased anterior de- 

 velopment of the cerebrum, present 



an increased angle, whilst the occi- 

 pital lobe is much reduced, two 

 deep fissures dividing its superior 

 and middle portions. The superior 

 connecting convolution (pli de pas- 

 sage) in Semnopithecus is largely 

 developed and entirely superficial, 

 and in consequence of the fissure 

 being obliterated the operculum is 

 not developed at its superior part. 

 The second connecting convolution 

 is not obvious. 



M. Gratiolet was unable to ex- 

 amine the internal face of the 

 cerebral hemisphere in the Semno- 

 pitheci on account of the specimens 

 he had at hand being few in number. 

 I have opened the brain in my pos- 

 session, and an outline of its internal 

 folds and fissures is given in Fig. 2 : 

 a is the convolution of the external 

 zone divided by a deep fissure from 

 b, the convolution of the internal 

 zone, and c, the quadrilateral lobe ; 

 d is the internal occipital lobule ; 

 e the fissures of the hippocampi ; 

 f the inferior temporal fold, and g, 

 the middle internal temporal fold ; 

 h is the " pli godronne." The 

 quadrilateral lobe is of larger size 

 than in the Cercopitheci ; the occi- 

 pital lobule is smaller, and the 

 fissures of the hippocampi are much 

 simpler and straighter. There is 

 also about the posterior surface a 

 greater freedom from plication, and 

 a more definite separation of the 



occipital lobule and temporal folds 

 than in the Cercopitheci. Now 

 from his extensive researches on 

 the cerebral anatomy of Quadru- 

 mana, M. Gratiolet has been led to 

 lay down the following law : That 

 the higher a monkey is in the 

 series leading up to man, the larger 

 will be the development of the 

 quadrilateral lobe, and the greater 

 the simplicity of the fissures of the 

 hippocampi, and vice versa. Hence 

 the examination of the internal 

 surface of the cerebral hemispheres 

 of Semnopithecus confirms their 

 position above Cercopithecus ; since 

 it shows that they present charac- 

 ters entirely coinciding with M. 

 Gratiolet's statement deduced from 

 the study of other brains. It may 

 be well here to give the external 

 characters also, which according to 

 M. Gratiolet's most trustworthy de- 

 ductions, determine the relative 

 position of a brain in the simious 



