180 STRUCTURE AND CLASSIFICATION OF BIRDS 



of the normal fashion ; the Trachephonse are those in which 

 the last rings of the trachea are much modified, and the 

 syrinx may be termed tracheal. 



The Mesomyodi with a tracheobronchial syrinx comprise 

 representatives from both the Old and the. New Worlds. In 

 them the syrinx presents a varied form, coupled with the fun- 

 damental resemblance indicated. Johannes Mullee has 

 figured and described a number of genera. Gaeeod has 

 figured and described others. In Lipaugus cineraceus (of 

 the family Cotingidse) the intrinsic muscle is of great width, 

 which seems to foreshadow its division in the Oscines into a 

 complex of muscles ; it is attached to the third bronchial 

 semi-ring. 



The first and second bronchial semi-rings resemble the 

 tracheal in their flatness, depth, and close approximation. 

 Those which follow are slightly ossified throughout. In 

 Heteropelma and GhiromachcBris, which are Pipridse, the 

 syrinx is very similar. In Pipra leucociltm the intrinsic ' 

 muscle has a tendency to split into two, a further approxima- 

 tion to the Oscines. In Hadrostomus aglaia; a cotingid, the 

 wide and thin intrinsic muscle is attached to the first bron- 

 chial semi-ring. This semi-ring is close to the last tracheal 

 ring, and is like it in structure, being deep. The next 

 bronchial semi-ring is separated by a considerable interval, 

 and the third by a wider interval still, from the ring in 

 front. 



In the Madagascar Philepitta, which Foebes ' was the 

 first to refer definitely to the present group of passerines, the 

 structure in some respects recalls that of the Euryleemidse. 

 The manubrium stemi is but slightly bifid ; but it has in 

 the normal passerines no vinculum. The syrinx, on the 

 other hand, differs from the Ol'd- World Mesomyodi by the 

 details of its structure (see figs. 87, 88). The different arching 

 of the bronchial semi-rings leaves great membranous spaces 

 in the wall of the syrinx. The first two semi-rings are very 

 concave upwards ; the two following are not so markedly 

 concave ; the next is concave in the reverse direction. The 

 ' ' On some Points in the Structure of Philepitta,' <fec., P. Z S. 1880, p. 387, 



