Account of Observed Forms of Larynx. 33 



process of tlic broncbi, or what here will henceforward be called the processus vocalis of the 

 tracbeophone larynx. It is not in close relation with the vibrating portion of the 

 trachea, but lies free on its sides ; to its shai-p end, which reaches as far as the upper 

 end of the tracheal larjTix, is attached the end of the lateral muscle of the trachea, and 

 when these muscles are in action aud pull on the processus vocales of the bronchi, the 

 membranous portion of the trachea is contracted, and the numerous fine vibrating half- 

 rino-s are brought close together. The musciili sternotracheales arise in this genus, and 

 in all that follow, not from the trachea, but from the points of the processus vocales'^. 

 In the membranous portion of the trachea, there are, in both its anterior and posterior 

 flattened walls, very many fine half-rings. The three lowest are somewhat stronger and 

 are in connection with the j^rocessiis vocales, the succeeding half-rings vibrate, and the 

 ends of these half-rings are inserted into the lateral bands of the membranous portion of 

 the trachea. In all, the membranous portion of the trachea has thirteen fine thin 

 half-rings in its anterior wall, and a similar number in its posterior. 



Species examined Cliamaeza memloides Vig. 



Grallaria Vieill. also belongs, without doubt, to this group, which is only separated 

 from Chamaeza by the absence of plates on the hinder side of the foot. I have not, 

 however, examined Grallaria. 



Scytalopus Gould. This genus also has the high pyramidal processus vocales on the 

 first broncbial rings, from the points of which the musculi sternotracheales arise, and which 

 are drawn up to the strong rings of the trachea by other muscles. The vibrating half-rings 

 of the trachea are of the form common in this family. I examined Scytalopus indlgoticus 

 [Myiothera indigotica Pr. M.). 



This genus, which is closely allied to Pteroptochus, is with I'teroptoclius, distinguished 

 from all previously mentioned, and all succeeding genera which possess the tracheal larynx, 

 by the two deep notches on either side of the sternum; and since the feet of Scytalopus 

 and Pteroptochus are covered with two series of large plates on the hinder surface (as in 

 Thamnophllus and Chamaeza), it is probable that Pteroptochus also possesses the same 

 tracheal larynx, and so it can with great probability be placed in this family, although 

 Eyton's anatomical note on P. tarnii does not allow us to form any conclusions as to 

 the existence of any tracheal larynx. 



' An instance, as observed by me in many other birds, that the musculiis sferuotrachealis is not produced to 

 the sides of the trachea (Cuvier), but rather that the lateral muscles of the trachea and the sternotracheales are 

 different muscles. 



