208 



MERISTIC VARIATION. 



[part I. 



instead of being posterior to it as usual. Outside this tooth is 

 another, standing out of the arcade, having the size and almost the 

 form of normal m\ B. M., 749, c. (Fig. 39). 



This case may be an example of one of two principles which 

 will be in the next chapter pointed out as operating in the case 



Fig. 39. Mycetes niger, No. 206; right upper molars. Brit. Mus., 749, c. 



of dental Variation. Either wi s may have divided into two, both 

 standing in series, and the normal rn? may have been pushed out 

 of the arcade in connexion with this reduplication ; or the tooth 

 standing outside may represent an addition to the normal series, 

 and in that case the tooth standing as m 3 in the series may be a 

 representation of m s , raised to the normally higher condition of m- 

 in correlation with the presence of an extra tooth in the series, in 

 the way shewn to occur in other cases (see Chapter x., Section 7). 

 Between these alternative possibilities I cannot decide. 



Supernumerary premolar. 



207. Mycetes niger : between and internal to p}_ and l^ on left side there is a 

 premolar. This is probably a supernumerary one, but the jaw is so much diseased 

 that the relations are not distinct. B. M., 749, d. 



208. Callithrix, normal adults, 22. (In B.M., 51, b on both sides m? is separated 

 by a narrow diastema from w*, The appearances suggest that possibly a small 

 rudimentary tooth may have stood between them, but this is quite uncertain). 



Nyctipithecus : 1 1 normals. 



209. Pithecia : 11 normals. 



Specimen having no right w^, and apparently this tooth was not 

 about to be formed, for the dentition is otherwise complete. C. M., 

 1094, a. (Cp. No. 202.) 



Lagothrix, 6, Chiropotes, 1, Ouakaria, 3 normals respectively. 



Hapalid^:. In this group m 3 is normally absent : and no 

 specimen having this tooth or any other dental abnormality was seen. 

 Of adult normal skulls 33 were seen, belonging to various species. 





