PEELIMINAEY REMARKS. 15 



poorness of the material at hand, which, although sufficiently perfect to be 

 readily distinguished by a practiced eye familiar with the associated forms, is 

 not good enough to permit figures of them to be made which would enable 

 others to identify them. Consequently this monograph can not be said to 

 be entirely complete. 



In dealing with the different species and genera previously described, 

 I have endeavored to ascertain their true nature as far as possible from 

 the type specimens when they could be found, and have adopted them 

 wherever it seemed reasonable. Comments on many of them will be found 

 in the text of the volume, where I give my reasons for adopting or rejecting 

 them. 



