PREFACE TO THIRD EDITION. 9 



of the ordinal and subordinal groups of birds. It was at first the 

 intention of the Committee to modernize the sequence of these groups. 

 The fact, however, that present systems of classification in ornithology 

 are admittedly tentative, and differ widely among themselves, it seemed 

 best, from the standpoint of convenience, to continue the old Cheek- 

 List system unchanged, since the users of the Check-List are familiar 

 with the present order of arrangement and would regret the annoyance 

 that a radical change from it would cause. In deference to this 

 known wide-spread preference the old order of arrangement has been 

 continued. In the opinion of the Committee, a slight modification' 

 of the system proposed by Dr. Hans Gadow in 1892-93^ would best 

 reflect our present knowledge of the classification of birds, an abstract 

 of which is here added. This system is at present extensively em- 

 ployed, it being that followed by Evans in the volume 'Birds' of the 

 'Cambridge Natural History Series' (London, 1899), and by Knowl- 

 ton in his recently published 'Birds of the World' (New York, 1909). 

 It is also the basis of the system adopted by Ridgway in his 'Birds of 

 North and Middle America.' The subjoined abstract of the Gadow 

 system is from Bronn's 'Thier-reichs'. The Check-List equivalents 

 are added in brackets, for convenience of comparison. 



Abstract of Gadow's Classification of Birds. 



Class AVES.« 



Subclass I. Ahch^ornithes. 

 Subclass II. Neornithes. 



Division I. Neornithes Batite. 

 RatitcB. 



Struthiones. 

 Rheas. 



1 It is believed, tor example, that the groups Columbse, Striges, and Pslttaci should be 

 accorded ordinal rank; and in general the Committee would prefer the Check-List eval- 

 uation of the groups therein recognized as orders and suborders. 



2 On the Classification of Birds. By Hans Gadow, M. A., Ph. D., F. Z. S., Strickland 

 Curator and Lecturer on Advanced Morphology of Vertebrata in the University of 

 Cambridge. — Proc. ZoBl. Soc. London, 1892, pp. 229-256. 



Dr. H. G. Bronn's Klassen und Ordnungeu des Thier-reichs, wissenschaftllch darges- 

 telt in Wort und Bild. Sechster Band. Vierte Abtheilung. VSgel. Von Hans Gadow, 



Ph. D., M. A., F. R. S II, Systematischer Theil, Leipzig, 1893.— Roy. 8vo, pp. 



vii -I- 304. 



' Subclass I, and Divisions 1 and 2, and Order 1 of Division 3, consist wholly of extinct 

 types, and are not included in the classification, adopted in the Check-List, given above 

 in the ' Table of Contents '. 



