CATALOGUE 



BIRDS. 



Older II. PASSERIPORMES 



(Cat. B. vol. iii. p. 1). 



Suborder I. PASSERES 



(Cat. B. vol. iii. p. 1). 



Division II. MESOMYODI 



(Cat. B. vol. xiv. p. 1). 



Subdivision II. TRACHEOPHON^ 



(Cat. B. vol. xiv. p. 1). 



The Tracheoplioncp are Passeres in which, contrary to what occurs 

 in the normal members ol: this group, the lower end of the trachea 

 is specially modified in order to form an organ of voice, and the 

 bronchi are not involved in the arrangement at all. 



This peculiar structure was described by the great anatomist 

 Johannes Miiller, by whom it was first discovered, as follows : — 



" The lower end of the trachea is flattened anteriorly and poste- 

 riorly ; its walls are thin and membranous and contain extremely 

 fine anterior and posterior half-rings, which are fastened at the sides 

 by long elastic bands. The position of these half-rings is altered by 

 the muscles attached to their sides. In all these birds the cartila- 

 ginous pessuJus in the furcation of the trachea is wanting, and is 



VOL. XV. B 



