30 



THE LOWER PRIMATES 



and indicates in a general way the position of the inferior frontal sulcus of the 

 higher primates. A faint indentation on the boundary between the parietal 

 and the frontal lobes marks the position of the sulcus centrahs, but no 



Courlc.sv. American Museum of Na!ural Hislory 



FIGS. 8 AND 9. HAND AND FOOT OF LEMUR MONGOZ. 

 Left. Palmar surface of hand showing digitation, palmar creases, phalangeal pads and opposable thumb. 

 Right. Plantar surface of foot showing plantar creases, digitation, long toes, plantar pads, distal phalanges 

 and opposable great toe. 



lissural marking corresponding to the sulcus simiarum or any occipital 

 marking on the lateral aspect of the brain is apparent. In fact, such expansion 

 as has occurred in the differentiation of the occipital lobe confines itself 

 almost exclusively to the mesial surface of the hemisphere. This primitive 

 development of the occipital lobe leaves a large portion of the cerebellum 

 still uncovered bj' the overhanging cerebral hemisphere. It thus determines a 

 condition intermediate between the cerebral development in all the monkeys 

 and apes (in which the cerebellum is completely overhung by the cerebral 

 hemisphere) and in lower mammals such as the carnivores (in which the cere- 



