260 THE DENTAL SYSTEM OF THE PRIMATES [SECT. A 



the anthropoid apes. In spite of this, the tubercle need not indi- 

 cate a progressive evolutionary phase, for Osborn identifies it with 

 a cusp called by him the protostyle, and observed in many of the 

 lower mammals. 



MOLAR TEETH. 



Additions to the number of molar teeth may be by way of 

 gemination, of which a good instance exists in an European skull 

 (from Paestum) in the University Museum of Anatomy, while a 

 striking instance is shewn in Fig. 194, which represents gemi- 

 nation in the last molar tooth in the mandible of an adult Orang- 

 utan. The original specimen forms part of the Selenka Collection 

 at Munich. 



Among the Anthropoidea, supernumerary molar teeth occur 

 with some irregularity in the various " families " concerned. This 

 statement arises from the consideration of the records collected by 

 Zuckerkandl (quoted by De Terra, op. cit.). 



Thus for instance in the Cebidae, the genus Ateles provides 

 more examples than either of the genera Cebus or Mycetes. But 

 in all these cases the accessory tooth is regarded as a fourth 

 molar, and it is situated in the upper jaw. 



Passing to the Cercopithecidae, again it appears that accessory 

 molar teeth are very infrequent. The same remark applies to the 

 Hylobatidae among the Simiidae, for no instance was observed in 

 a collection of fifty-one crania of that genus. 



The Orang-utan provides by far the greatest number of records 

 among the larger Simiidae, the Gorilla coming next, and the 

 Chimpanzee last in this sequence. Thus in the Orang-utan (cf. x, 

 Fig. 195) the frequency of occurrence in the male sex amounts to 

 nearly 50 °/ (for the Gorilla the corresponding figure is about <S ). 



This statement is based on the examination of the very large 

 collection (more than 200 crania) at Munich, in the course of 

 which the very remarkable example shewn in Fig. 196 was dis- 

 covered. In this example four fully-formed molar teeth are seen: 

 behind the last of these is an aborted dental mass, and behind 

 this a depression which had probably contained yet another dental 

 mass. 



