XIV PREFACE TO FOURTH EDITION. 



melodia, differs in no way from the others in rank and is "typical '" 

 of nothing, being simply the first race to be described. It often 

 stands properly in the middle of a series of races and the only 

 reason for its appearance so often at the head of the group is that 

 it was usually the eastern race, the one with which our geographic 

 series generally begins, that was the first to be named. 



Hypothetical List. This list has been the receptacle for various 

 described species that for one reason or another have been with- 

 held from the main text. In the present edition it has been 

 thought best to list all forms that have at any time been referred 

 to it with an explanation of their subsequent disposition. In 

 future it would seem advisable to restrict the hst to (1) described 

 species of which no specimen is extant and which it has been 

 impossible to identify with any known form; (2) species of which 

 a specimen is preserved but which appear to be cases of erratic 

 individual variation; (3) named species which are now regarded 

 as hybrids or cases of melanism. Curiously enough there are a 

 number of specimens belonging to the last category upon which 

 names have been based, which have never been mentioned in the 

 "Hypothetical List." (4) Well estabhshed species the alleged 

 occurrence of which within our limits is open to question. 



Fossil List. The list of fossil birds in the present edition of the 

 Check-List is entirely the work of Dr. Alexander Wetmore who 

 besides bringing the subject up to date has added all recent spe- 

 cies which have occurred also as fossils, thus adding much to the 

 value of the List. 



Summary of Changes. It has been customary to publish a sup- 

 plement to the Check-List embodying the changes and additions 

 made in the preparation of a new edition, but it was thought 

 better in view of the length of time that has elapsed since the 

 appearance of the last edition to publish this information as an 

 appendix to the List itself where it will be easily accessible to those 

 who use the work and who desire to know why changes have 

 been made in names or what species or subspecies have been 

 added to the List. The chairman is responsible for the arrange- 

 ment and compilation of this Summary, as time did not permit 

 of its being submitted to the Committee before being put in type. 

 Every name occurring in the last edition of the Check-List will 

 be found in the Index to the present edition with a page reference 



