SKELETON OF QUADRUMANA. 55 i 



longitudinal, extent than in Man, and chiefly differs in the con- 

 vexity of the articulation for the hallux, which articular surface in 

 Man is nearly flat : this difference is very significative of the dif- 

 ferent function of the hallux in the two species ; the chief fulcrum 

 of the foot requiring a firm articulation in Man, but in the Gorilla 

 great extent of motion for the functions of an opposable grasping 

 thumb. The metatarsal of the hallux is fully as large as that in Man ; 

 it differs in the deeper concavity of the proximal articular surface, 

 and in the more prominent convexity of the distal one. The 

 proximal phalanx of the hallux also equals that of Man in size ; 

 the borders of its proximal concavity are less neatly defined. The 

 ungual phalanx is somewhat less than that of Man, especially in 

 its terminal rough tuberosity ; it is concave below instead of being 

 convex. The remaining metatarsals of the foot are much longer 

 and stronger than in Man ; the upper border is more bent. The 

 first and second phalanges are larger and more bent. The ungual 

 phalanges are longer and narrower in proportion than in Man. 



In all the characters by w^hich the bones of the foot of the Go- 

 rilla depart from the Human type, those of the Chimpanzee recede 

 in a greater degree, the foot being in that smaller ape better 

 adapted for grasping and climbing, and less for occasional upright 

 posture and motion upon the lower limbs. The lever of the heel 

 is relatively shorter and more slender ; the hallux has still more 

 slender proportions, and the whole foot is narrower in proportion 

 to its length, more curved towards the planta, and more inverted 

 in the Chimpanzee. 



On a retrospect of the skeletons of the latisternal tailless 

 Catarrhines, it may be observed that no Orang, Chimpanzee, or 

 Gibbon has mastoid processes ; they are present in the Gorilla, 

 but smaller than in Man. In the Chimpanzee, as in the Orangs, 

 Gibbons, and inferior Simice, the lower surface of the long 

 tympanic or auditory process is more or less flat and smooth, 

 developing in the Chimpanzee only a slight tubercle, anterior to 

 the stylo -hyal pit. In the Gorilla the auditory process is more 

 or less convex below, and developes a ridge, answering to the 

 vaginal process, on the outer side of the carotid canal. The 

 processes posterior and internal to the glenoid articular surface, 

 especially the internal one, arc better developed in the Gorilla 

 than in the Chimpanzee ; the ridge which extends from the 

 ectopterygoid along the inner border of the foramen ovale ter- 

 minates in tlic Gorilla by an angle or process answering to that 

 called ' styliibrm ' or ' spinous ' in Man, but of which there is no 

 trace in the Chimpanzee, Orang, or Gibbon. 



