chap, ix.] TEETH : PRELIMINARY. 199 



zoological position of the groups concerned. In several cases 

 variations of similar nature were seen in different groups ; cases of 

 this kind will be brought into association in the next chapter. 



As regards nomenclature I have in the main followed the 

 common English system, numbering both the premolars and 

 molars from in front backwards. In one respect I have departed 

 from the practice now much followed. It has seemed on the whole 

 better that the premolar which in any given jaw stands first, 

 should be called p 1 , even though in certain cases there may be 

 reasons for doubting whether it is the true homologue of the p 1 of 

 other cases 1 . Theoretical views of this kind can only at best be 

 used as a substitute for the obvious nomenclature in a few re- 

 stricted cases, such as that of the Cat, in which by the application 

 of the methods of reasoning ordinarily adopted in Comparative 

 Anatomy the first upper premolar would be looked on as the 

 equivalent of F 2 in the Dog. There are, however, few who would 

 feel confident in extending this reasoning to many other cases, 

 that of Man, for instance, and I believe it is on the whole simpler 

 to number the teeth according to their visible and actual relations. 

 As I have already attempted to shew in another place 2 , in the light 

 of the facts of Variation, it is to be doubted whether in their varia- 

 tions teeth do follow those strict rules of individual homology by 

 which naturalists have sought to relate the arrangements in dif- 

 ferent types with each other. 



The material examined has consisted chiefly of specimens in 

 the British Museum and the Museums of the College of Surgeons, 

 Leyden, Oxford and Cambridge, the Paris Museum of Natural 

 History, and some smaller collections. I have to thank the 

 authorities of these several museums for the great kindness I 

 have received from them; and in particular I must express my 

 indebtedness to Mr Oldfield Thomas, of the British Museum, for 

 the constant help and advice which he has given me, both as 

 regards the subject of teeth generally and especially in examining 

 the specimens in the British Museum 3 . 



PRIMATES. 



SoniDyE. The Anthropoid Apes (Orang, Chimpanzee, and 

 Gorilla). 



165. The teeth of the three large Anthropoids are perhaps more 

 variable, both in number and position, than those of any other 



1 In cases where confusion might arise any change from common nomenclature 

 is notified in the text. 



- Proc. Zool. Soc, 1892, p. 102. 



;! In the following descriptions B.M. stands for British Museum; C.S.M. for 

 Museum of the Royal College of Surgeons; CM., O.M., U.C.M., Leyd. M., P.M., 

 for the Cambridge, Oxford, University College London, Leyden and Paris Museums 

 respectively. 



