Prof. Owen on the Gorilla, 391 



upright attitude than those inferior anthropoid apes do." * This 

 inference has been fully borne out by the rest of tlie skeleton of the 

 Gorilla, subsequently acquired. 



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 stylohyal 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 are better developed, especially the internal one, in the 

 Gorilla than in the Chimpanzee ; the ridge which extends from the 

 ectopterygoid along the inner border of the foramen ovale, terminates 

 in the Gorilla by an angle or process answering to that called " sty- 

 liform " or " spinous " in Man, but of which there is no trace in the 

 Chimpanzee, Orang, or Gibbon. 



The orbits have a full oval form in the Orang ; they are almost 

 circular in the Chimpanzee and Siamang, more nearly circular, and 

 with a more prominent rim in the smaller Gibbons ; in the Gorilla 

 alone do they present the form which used to be deemed peculiar to 

 man. There is not much physiological significance in some of the 

 latter characters, but on that very account, the author deemed them 

 more instructive and guiding in the actual comparison. The occi- 

 pital foramen is nearer the back part of the cranium, and its plane 

 is more sloping, less horizontal in the Siamang than in the Chim- 

 panzee and Gorilla. Considering the less relative prominence of the 

 fore-part of the jaws in the Siamang, as compared with the Chim- 

 panzee, the occipital character of that Gibbon and of other species of 

 Hylohates marks well their inferior position in the quadrumanous 

 scale. 



In the greater relative size of the molars, compared with the inci- 

 sors, the Gorilla makes an important closer step towards Man than 

 does the Chimpanzee. The molar teeth are relatively so small in the 

 Siamang, that, notwithstanding the small size of the incisors, the 

 proportion of those teeth to the molars is only the same as in the 

 Gorilla : in other Gibbons {Hylobates lar), the four lower incisors 

 occupy an extent equal to that of the first four molars, in the Chim- 

 panzee equal to that of the first three molars, in the Siamang equal 

 to that of the first two molars and rather more than half of the third, 

 in Man equal to the first two molars and half of the third : in this 

 comparison the term molar is extended to the bicuspids. 



The proportion of the ascending ramus to the length of the lower 

 jaw tests the relative affinity of the tailless apes to Man. 



In a profile of the lower jaw, the author compares the line drawn 

 vertically from the top of the coronoid process to the horizontal length 

 along the alveoli. In Man and the Gorilla it is about i^ths, in the 

 Chimpanzee j^ths, in the Siamang it is only yV^is* "I'he Siamang 

 further differs in the shape and production of the angle of the jaw, 

 and in the shape of the coronoid process, approaching the lower <S'mite 



* Transactions of the Zoological Society, vol. iii. p. 409. 



