INTRODUCTION. 



As anuounced in the lutroductiou to the fourteenth volume, the 

 present yolume of the ' Catalogue of Birds ' is devoted entirely to 

 the Tracheophonine Passeres, that is to those Passerines in which 

 the organ of voice is formed by a special modification of the lower 

 end of the trachea, as more fully described below. According to 

 Garrod's arrangement, which is followed here, the Tracheophonne 

 form a subdivision of the Mesomyodce, although, from my own point 

 of view, it would seem better to separate the Passeres into four 

 suborders of equivalent value, of which the Tracheophonce should be 

 considered the lowest and most abnormal. This, however, is not a 

 point of material consequence. Whichever view is taken, the Tra- 

 cheophonce remain as an independent group of Passeres absolutely 

 distinguished from their fellows by the peculiar modification of 

 their trachea, although, with external characters only to rely upon, 

 it is in some cases difiicult to separate them from corresponding 

 forms of the Oscines and Oligomyodcv. 



So far as has been hitherto made out, the Tracheophonine struc- 

 ture prevails only in four families of Passerine Birds, all of which 

 are absolutely restricted to the Neotropical Region. In the Neo- 

 tropical Region, however, TrctcheojiJiome are abundant and widely 

 spread, except in the Antillean Subrcgion, where they do not 

 occur. 



The great anatomist Johannes Miiller was the discoverer of the 

 Tracheophonine structure. Little additional light was thrown upon 

 the subject until the researches of Garrod were commenced many 

 years later. Gan'od fully recognized three of the families of this 



