482 STRUCTURE AND CLASSIFICATION OF BIRDS 



unless, indeed, their homologues exist l in the form of a 

 muscular covering to the terminal purely membranous 

 section of the bronchus (fig. 229) which, dividing into three 

 slips, runs from thence to the parietes. There are in any 

 case no muscles at the actual bifurcation. Nor is there any 

 change in the character of the rings themselves such as to 

 suggest even the rudiment of a syrinx. In Cathartes 

 the rings at the bifurcation are extraordinarily thin, leav- 

 ing wide membranous intervals, which are occasionally 



O * 



traversed by bridges putting successive rings into communi- 

 cation. In Sarcorhamphus and GyparcJms, which also agree 

 (see below) in their 'muscle formula,' the rings are thicker 

 and closer together (see fig. 229). And in these two genera 

 the bronchi are incomplete internally, giving rise to what 

 may be termed a membrana tympaniforrnis. 



In GyparcJms papa the tendons of the patagium are 

 somewhat complicated. The brevis consists of a separate 

 anterior and posterior section, of which the latter is thinner 

 and more diffuse. The anterior tendon divides into two, 

 of which the foremost gives off a slip to the longus. There 

 is no biceps slip. The tendons, in fact, are thoroughly 

 stork-like, as are those of the condor (Sarcorhamphus) 

 and Cathartes. In this character the family is very uni- 

 form. 



The expansor secundariorum is present in all. 



The pectoralis primus is well divided into two parts, of 

 which the lower (in G. pa23a) is inserted by a thin round 

 tendon altogether below insertion of superficial layer. The 

 head of the anconceus is distinctly bifid and entirely tendinous, 

 arising from scapula and from supinator muscle. There is 

 a humeral slip of moderate size. (This muscle is described 

 from Cathartes.) 



The anibiens is present in all Cathartidae ; so too the 

 semitendinosus and its accessory. Cathartes has in addition 

 the femorocaudal, which is absent in the other genera. In 

 GyparcJms ( ? as to the others) the semitendinosus and semi- 



1 BEDDAKD, ' Notes on the Anatomy of the Condor,' P. Z. S. 1890, p. 146. 



