i62 PRIMARY FACTOliS OF ORGANIC EVOLUTION. 



peculiar form of the posterior face of the mandibular 

 symphysis, already pointed out by Topinard in the jaw 



of Naulette. On these characters the following re- 

 marks may be made.^ 



I. The prominent superciliary crests, which are 



i^ Archives Beiges de Biologie, VII., 1886, p. 731, Gand. 



