27 
generically, it is not easy to indicate, but all those with prognathous 
crania may be safely excluded. It is improbable that Mongolian 
races will early participate in such a modification, as they 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 Hominide 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 zodlogy, 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 clistinct species. The genera 
of Hominide will then, if the characters become constant, be as 
follows:— 
1.3; C. >; Pm. 3; M. §; Homo. 
T. 3; C.4; Pm. 2; M. 3; Metanthropos. 
1.3; C.4; Pm. 3; M. 3; Epanthropos. 
