XVI rt^TRODUCTION. 



criticism, that I have failed to identify them with those ah'eady in the books. 

 In explanation of this, I would say that I have defined the tribes, genera 

 and species, in many instances, by characters, which. have been unnoticed 

 or neglected bj^ previous investigators ; and finding that quite frequently, 

 species, having a strong external resemblance, differed by structural charac- 

 ters of great moment, I did not feel warranted in applying to them names 

 given to species, which agreed with them in the outline, vestiture and 

 sculpture of the larger parts of the body, but which have been described 

 from other zoological districts. It will be easy, by the aid of the structural 

 characters which I have given, to identify my species with the types exist- 

 ing in European cabinets. I would rather that those I have named would 

 sink into synonymy, than that, in the present condition of science, I should 

 appear to teach false ideas regarding geographical distribution, which, Avhen 

 carefully studied, must give us important aid in attaining a knowledge of 

 the causes and develoijment of the existing order of things. 



