INTRODUCTION. 



My ornithological studies having been principally devoted to South- 

 American Birds, I had little hesitation in acceding to Dr. G anther's 

 request that I should prepare the Catalogue of the Mesomyodian 

 Passeres in the Collection of the British Museum. Of the thirteen 

 families that belong to this section of the Passerine group, nine are 

 exclusively Neotropical, and these nine families embrace by far the 

 greatest number of specific forms, the four Mesomyodian families 

 as yet recognized in the Old World being comparatively insig- 

 nificant in point of numbers. My subject was, therefore, sufficiently 

 familial to me. 



At the same time some of the groups to be treated of — I may 

 point especially to the Tyrannida — are universally allowed to be 

 amongst the most difficult portions of the class of Birds for satis- 

 factory determination. I felt, therefore, that in the short time 

 that could necessarily be allowed me for the completion of my task 

 I had no easy duty to perform. 



The Mesomyodian Passeres, according to Garrod's arrangement, 

 fall readily into two great sections, in one of which the syrinx 

 remains nearly as in the typical Oscines, but with a lesser number 

 of singing-muscles ; while in the other, as first shown by the great 

 anatomist Johannes Miiller, the lower end of the trachea is specially 

 modified to form an organ of voice. In the present volume the 

 forms belonging to the first of these sections (Oligomyodw) are 

 treated of. They are here arranged in nine families, the first five 

 of which belong exclusively to the New World, while the last four 

 are restricted to the three Southern regions of the Old World. 



In dealing with the five Neogean families — Tyrannida', Oxy- 

 rhamphidce, Pipridoe, Cotingidce, and Phytotomida — I have followed 

 throughout, with very few exceptions, the divisions and arrange- 



