AND AFFINITIES OF THE GORILLA. 279 



In former memoirs I selected the best-preserved conditions of the dental series in 

 adult males of Troglodytes Gorilla and Troglodytes niger, in expectation of demonstra- 

 ting beyond cavil, by the important characters of dentition, the generic affinity of the 

 Gorilla and Chimpanzee, and their relative position in such genus. 



In Memoir III., for example', plates 61 and 68 show the large proportion of the 

 canines to be no generic peculiarity of the Gorilla, but to characterize almost equally 

 the adult males of both Gorilla and Chimpanzee : even a specific difference can 

 hardly be predicated of the two Apes in this respect. Plates 60 and 63 show their 

 correspondence in the almost transverse arrangement of the four incisors ; and, also, the 

 specific distinction of the Gorilla in the smaller relative size of those teeth, and its 

 resultant higher grade in the genus. The diastema between the incisors and canines is 

 greater in the Chimpanzee than in the Gorilla, in the two skulls of the males figured. 



With respect to the lower molars, I would request a reference to my Memoir, No. V.'^ 

 plate 32. In both Gorilla and Chimpanzee the outer balf of each molar is divided into 

 three tubercles, the third being situated towards the middle of the back part of the 

 crown, but so as to show it to belong to the outer rather than to the inner moiety of the 

 crown : it is superior in size and distinctness in the last molar of the Gorilla than in that 

 of the Chimpanzee, making the fore-and-aft extent of the crown greater in proportion 

 to the breadth. The portion of ' cingulum ' at the back part of the crown is developed 

 into a small accessory cusp, more distinctly in the Gorilla, and yet also present in the 

 Chimpanzee. In neither, however, is it so large or so shaped as the true 'talon' in 

 the last lower molar of Macacus : it does not form part of the grinding-surface of the 

 tooth. Every zoologist may discern the essential similarity of structure, under the slight 

 difierence of proportion, in the last lower molar of the Chimpanzee and Gorilla ; and I 

 believe the majority will concur in my estimate of the value of the differences between 

 the lower true molars in Troglodytes Gorilla and Troglodytes niger. The most important 

 facts which the above-cited Memoir (V.) and plates elucidate are those which show 

 the resemblance of the pattern of the grinding-surface of the true molars in the genus 

 Troglodytes to that in Homo, at least as it is manifested in the large grinders of an 

 Australian aboriginal (plate 31. fig. 3). 



On the above-stated grounds, therefore, I refer the Gorilla to the genus Troglodytes, 

 Geoffr., to a distinct species (T. Gorilla, Sav.) in that genus, which species in the 

 serial order I place above the Chimpanzee (T. niger, Geoffr.). The genus Troglodytes 

 belongs to the ' dasvpygal ' section of the ' iatisternal ' tribe of tailless, catarrhine 

 Quadruraana, and, in that section, ranks above the genus Pithecus, Geofl^r. The 

 Quadrumana are ' gyrencephalous,' and have an ' ordinal ' distinction in their subclass, 



' " Osteological Contributions to the Natural History of the Chimpanzees \Trogloihjtes, Geoffr.), including 

 the description of the skull of a large species {Troglodytes Gorilla, Savage>," Trans. Zool. Soc. iii. 18-18. 



' " Osteological Contributions, &c., No. 5 : Comparison of the Lower Jaw and Vertebral Column of the 

 Troglodytes Gorilla, Troglodytes niger, Pithecus Satyrus, and different varieties of the Human Race," Trans. 

 Zool. Soc. iv. 1851. 



