194 PROCEEDINGS OP THE ACADEMY OP " [1879. 



genericalby, it is not easy to indicate, but all those with prognathous 

 crania may be safely excluded. It is improbable that Mongolian 

 races will earl} 7 participate in such a modification, as the}' have a 

 tendency to prognathism, and a generally strong dental develop- 

 ment. 



Since the reduction in the number of teeth is intimately connected 

 with orthognathism, it is easy to suppose that it is primarily due to 

 the diminished space allowed by the contracted maxillary arcade. 

 This contraction is doubtless due to a deficiency of building mate- 

 rial, consequent on a transfer of force to some other part of the 

 structure during the period of growth. This transfer may be to 

 the superior parts of the cranium, which is extended to contain an 

 enlarged brain. As the loss of a tooth from each side has so far 

 been sufficient to accommodate the dentition to the space which 

 it is to occupy, it is not likely that the absence of both I. 2, and 

 M. III. will become established. The reduction in the inferior 

 series is less, and I do not know of any examples of the absence 

 of the external incisors of the lower jaw. The loss of the third 

 inferior molars is, on the other hand, very common. It then may 

 be reasonably maintained that two genera of Hominidse will be at 

 some future day added to Homo; that the latter will include the 

 inferior races of men, and the future the superior; that, although 

 in specific characters there may be a want of greater constancy in 

 the species of the new genera as compared with each other than 

 as compared with the primitive and true Homo, they will pre- 

 sent cases of what is elsewhere known in zoology, that the 

 same or nearly the same specific characters may be found in dif- 

 ferent genera. Under such circumstances the form referred to a 

 new genus becomes at the same time distinct species. The genera 

 of Hominidae will then, if the characters become constant, be as 

 follows: 



I. |; C. |; Pm. ; M. ; Homo. 



I. ; C. {; Pm. ; M. ; Metanthropos. 



I. f ; C. i; Pm. ; M. ; Epanthropos. 



