29ti THE DENTAL SYSTEM OF THE PRIMATES [SECT. A 



The tritubercular theory has been discussed at greater length 

 than the other views, partly because of its special applicability 

 to the Hominidae, and also because of the very important 

 inferences based upon this by Cope and set forth by him in the 

 American Naturalist (1893), and again, at a later date, in the 

 Primary Factors of Organic Evolution (1896). 



The molar teeth are the special object of study, and Cope and 

 Topinard agree in declaring that the Hominidae, and especially 

 the more highly civilized among recent Hominidae, are tending 

 by reversion towards the condition of trituberculy in the upper 

 molars, the hypocone (cf. Fig. 207, "PI") tending to disappear. 

 Topinard (L'Antltropologie, 1892) gives some striking statistics 

 from a research on several hundred crania, and has drawn up 

 comparative tables illustrative of the tendency in the several 

 human races (cf. also Tomes' Dental Anatomy, 1914). Both Topinard 

 and Tomes appear to ignore the earlier work of Zuckerkandl and 

 Rose (cf. Chapter xiv). Tomes {op. cit. p. 597) gives a very 

 instructive tabulated statement illustrating Keith's researches 

 into the relative degree of cusp development in the European and 

 the Negro races, as well as in the higher apes. 



This tendency to trituberculy (which is undoubtedly demon- 

 strable) is considered by Cope 1 justification for the inference that 

 the Hominidae and Simiidae have descended directly fromLemurine 

 ancestors, to the exclusion of a " Cercopithecus stage " in the 

 genealogical history of these two families. (This inference is not 

 endorsed here.) Extinct Lemurs are appealed to, especially the 

 small animal known as Anaptomorphus (cf. Chapter xvn.), whose 

 nearest living relative is the very primitive Tarsius (cf. Chapter II.); 

 also the various representatives of the Genus Adapis (cf. Chapter 

 XVII.) which command a special interest in view of the features of 

 their lower incisor teeth. 



As was mentioned in the descriptive notes on the teeth of the Lemuroidea, 

 the true Lemurs are distinguished by the very peculiar procumbent position 

 and the extraordinarily styloid shape of their lower incisor and canine teeth. 

 The possession of this character would be an obstacle to the acceptance of 

 the view postulating the appearance of such Lemurine forms in the ancestry 



1 Haeckel and Klaatsch seem to be in agreement with Cope upon the general 

 accuracy of this account. 



