4 Bryant Walker 



have been described in many scattered publications not always accessible to 

 the student and not to be found except by laborious and time-taking search. 

 The convenience of a catalogue giving references to all of the new species 

 described since the Smithsonian monographs were published is obvious. 



In addition to such references, it has been deemed of service to add under 

 many of the species, old and new, the published opinions of many writers 

 as to their specific validity and relationships. It will be understood, of 

 course, that such quoted opinions are not necessarily those of the compiler 

 and are not endorsed by him unless expressly so stated. They are given 

 solely for what they are worth as representing the views of the author at 

 the time of their publication. 



The whole subject is brought down to May i, 1918. 



Bryant Walker. 



Dated July i, 1918. 



