248 THE DENTAL SYSTEM OF THE PRIMATES [SECT. A 



the comparatively gradual transition and transformation from one type of 

 tooth to another. 



ANTHROPOIDEA. Simiidae. Gorilla savagii. 



Dental formula: i, |; c, \ ; pm, §; m, § . (Figs. 174 and 175.) 

 In the replacement of the deciduous (milk) teeth by those of the per- 

 manent series it is to be noticed that whereas in the Hominidae the canine 

 teeth are replaced before the third molar tooth appears, yet in Gorilla 

 these events occur in the reverse order. In the male Gorilla (adult) the 

 canine teeth are enormously developed and the diastema is very evident. 

 The upper premolar teeth bear two cusps, labial and lingual in position, 

 but it is to be remarked that suggestions of two other cusps of minute size, 

 situated behind these, are not uncommonly present. The labial cusps are 

 the larger. The premolar teeth have three roots. The molar teeth are 

 quadricuspid and the cusps stand out with peculiar distinctness : the oblique 

 ridge joining the antero-internal and postero-external cusps is likewise un- 

 mistakeable. Measurements of a number of specimens shew that the last 

 molar tooth is smaller than the first, the second being the largest of the 

 three ; so that the reduction that has been so often noticed in the third 

 tooth is present in the dentition of Gorilla. The molar teeth are implanted 

 by three divergent roots. 



The lower premolar teeth differ not a little in appearance from one 

 another. The first is pyramidal and bears one well-defined cusp : in the 

 second tooth the two cusps are nearly equal in size, and behind them a 

 small talon projects. The molars are comparatively narrow, and elongated 

 antero-posteriorly : they commonly bear five cusps, the anterior pair of which 

 are to some extent united, and at the same time leave the three posterior 

 cusps isolated from one another. In some cases as many as six cusps 

 may be seen, the posterior part of the crown bearing four of these. No con- 

 firmation appears to be given to the statement that the postero-external cusp 

 is earlier affected by degenerated processes than the postero-internal cusp. 

 (v. ante, p. 244, footnote.) While the statement (cf. Topinard, quoted by 

 Fraipont, Archives de Biologie, vir. p. 735) as to the progressive increase 

 backwards in the size of molar teeth does not hold good in the upper series, 

 there is no doubt that it is true of the lower teeth 1 . 



ANTHROPOIDEA. Simiidae. Anthropopithecus Niger. 



Dental formula : i, § ; c, \ ; pm, § ; m, f . (Figs. 176 and 177.) 

 As regards the canine teeth similar remarks apply to the Chimpanzee and 

 Orang-utan. The upper premolar teeth, and indeed the whole dentition, of 

 the Chimpanzee suggest however the human dentition much more distinctly 



1 The latter statement as well as that made in reference to the relative sizes of 

 the molar teeth in the Orang-utan is based upon the results of measurement in 

 adult examples. Five male Gorillas and six male Orang-utans were available. 



