268 THE DENTAL SYSTEM OF THE PRIMATES [SECT. A 



these teeth presents this form in the Krapina specimens, added to 

 the fact of its appearance in the palaeolithic human teeth from 

 St Brelade's cave (in Jersey), leads to the conclusion that the 

 character in question is decidedly distinctive of a definite variety, 

 even if Ave deny to it the value of a specific character. 



III. Dental variations in situation. 



Displacement of teeth is rendered probable in cases in which 

 the space available for their implantation is diminished without 

 actual suppression of some of the teeth. This consideration 

 provides an explanation of many cases of the occurrence of teeth 

 in unusual situations, but is not altogether accountable for dis- 

 placements observed in certain instances among the black races 

 of the Hominidae, in which the jaws are large and the space 

 extensive. 



Again, the displacements observed in some skulls of Gorilla 

 are evidently not attributable to the factor of maxillary (or man- 

 dibular) reduction. 



The Anatomical Collection of Cambridge University includes 

 examples of dental displacements in crania of aboriginal natives 

 of Australia. In one such skull the canine teeth emerge on the 

 facial surface of the maxilla, and their direction has been so 

 altered that they lie in the horizontal rather than in the vertical 

 plane. The same Collection contains the cranium of an ancient 

 inhabitant of Peru, which presents a precisely similar condition of 

 the same teeth. Again, the third molar tooth may emerge on 

 the facial surface of the maxilla, immediately below the malar 

 process: instances of this have been seen in an ancient skull from 

 a cave in Jamaica : as also in the cranium of an aboriginal native 

 of Australia (in the possession of Dr Hacldon); while the same 

 condition obtains in the skull of an Orang-utan in the Museum at 

 Amsterdam. 



The incisor teeth are subject to similar variations in position. 

 Of these, perhaps the most striking are present in two crania 

 from the Melanesian island of New Britain : in each of these 

 specimens an incisor tooth has emerged, not on the alveolar 

 margin of the maxilla, but on the lower margin of the apertura 



