300 NEW YORK STATE MUSEUM 



the tracheal bifurcation unusually small. In Anas, Dafila, and Aix 

 the osseous tracheal rings are quite small, and the caliber of the 

 windpipe nearly uniform throughout its continuity. In M aril a 

 americana, however, this is changed, for in this species the 

 trachea is contracted at its upper end, and then gradually enlarges 

 to become of considerable size. It gradually contracts again along 

 the middle of its course, to enlarge again at its lower third and 

 finally becomes very small for about two centimeters above the 

 lower larynx. The firm osseous rings of this subcylindrical tube 

 show the lapping and locking process to perfection. The lower 

 laryngeal box is peculiar, being much compressed from side to side, 

 completely convex around its superior and lateral boundaries ; almost 

 entirely lacking in 'bone on its external aspect (this part having a 

 membranous drumhead stretched tightly over it in life), and ex- 

 hibiting fenestrae upon its mesial surface. It is of considerable size, 

 and projects above the lower bony larynx, against which it is closely 

 pressed mesially, and, as usual, communicates with it by an open- 

 ing below. Below this again, both the accessory organ and the 

 tracheal bifurcation open into another small, closed additional cham- 

 ber that is transversely disposed, and represents simply a distal 

 swelling of the common chamber, lying in front of and below the 

 bony pessulus. 



When Dr Sclater described the trachea of Metopiana 

 peposaca {$) in the Proceedings of the Zoological Society of 

 London [1868, p. 146], he said that "it has a large bulbous ex- 

 pansion of the windpipe." This was subsequently confirmed by 

 Garrod, who figured the trachea of this species in two views, 1 and 

 said of it that "the syringeal box is constructed on the same type 

 asinFuligula rufina and F. f e r i n a , being mostly com- 

 posed of membrane, and an interesting, oblique, simple osseous bar 

 running across near the upper margin of its outer side. There is 

 also some dilatation of the consolidated rings which go to form 

 the lower portion of the trachea ; this is to be observed on both the 

 right and left sides, the box being connected with the latter only. 

 In the female no box is developed. The trachea narrows slightly 

 above the syringeal box." In Garrod's figure of the air-passages of 

 the male Metopiana peposaca the peculiar expansion on 

 the trachea is 6y 2 centimeters above the lower syringeal expansion, 

 and appears to be nearly circular, with an average diameter of 

 about 2.8 centimeters. 



1 Coll. Sci. Memoirs, p. 282, 283. 



