xvi INTRODUCTION 



pithecus, (Pan), on the contrary, it is very richly convoluted. A 

 hippocampus minor is present in all Apes, and in some of the Cebhxe 

 it is much larger relatively than it is in Man, and is absolutely larger 

 than the hippocampus major. Of all Apes the Ourang has a brain 

 which is most like that of Man ; indeed it may be said to be like Man's 

 in all respects, save that it is much inferior in size and weight, and 

 that the cerebrum is more symmetrically convoluted and less com- 

 plicated with secondary and tertiary convolutions. If the brain of 

 Simia, (Pongo), be compared with that of Gorilla, and Anthropo- 

 pithecus, (Pan), we find the height of the cerebrum in front 

 greater in proportion in the former than in the latter ; also the 

 bridging convolutions, though small, are still distinguishable, while 

 they are absent in the Chimpanzee. Nevertheless the character cannot 

 be of much importance since it reappears in Ateles, ( !) while two 

 kinds of the genus Cebus (so closely allied as to have been sometimes 

 treated as one species) differ strangely from each other in this respect. 

 The corpus callosum in Apes generally, does not extend so far back as 

 in Man, and it is very short in Pithecia. In the Ourang and Chim- 

 panzee there are, as in Man, two corpora albicantia, while in the lower 

 Monkeys there is but one. The vermis of the cerebellum gives off 

 a small lobule, which is received into a special fossa of the petrous 

 bone. Certain prominences of the medulla oblongata, termed corpora 

 trapezoidea, which are found in the lower mammals, begin to make 

 their appearance in the Cebid^e." 



The number of pairs of ribs varies considerably among the genera 

 of the Primates. The Gorilla and Pan have thirteen; the Ourang 

 twelve same as Man ; Hylobates thirteen, but sometimes sixteen 

 (Flower and Lydekker) ; Colobus twelve; Pygathrix and Cercoce- 

 bus twelve, sometimes thirteen ; Lasiopyga and Erythrocebus twelve ; 

 Pithecus twelve, sometimes thirteen, (P. nemestrinus) ; Papio thir- 

 teen; Cynopithecus twelve; Magus twelve; Alouatta, Lago- 

 thrix, and Ateleus fourteen ; Cebus fourteen, but last pair very 

 short almost rudimentary in some species ; Pithecia twelve and thir- 

 teen (P. chiropotes) ; Callicebus and Callithrix twelve or thirteen ; 

 Aotus fourteen; Saimiri thirteen; Nycticebus sixteen; Perodicticus 

 fifteen. Of the vertebrae Pan, Pongo and Gorilla have 4 lumbar, 3 

 sacral, and 5 caudal ; Hylobates has 5 lumbar ; Colobus 7 lumbar, 3 

 sacral and 28 caudal ; Pygathrix 6 and 7 lumbar and 3 sacral ; Lasi- 

 opyga 6 and 7 lumbar, 3 sacral, 26 caudal ; Pithecus, Magus and 

 Cynopithecus 7 lumbar and 3 sacral, while Magus has 8 caudal, 

 and Cynopithecus has 5 ; Papio 6 lumbar and 3 sacral ; Alouatta 



