AMERICAN SWAN. 235 



from the furcula, when it becomes gradually cylindrical, reaches the curve 

 of the furcula, bends a little upwards, and enters a cavity formed in the 

 sternum, along which it passes to the length of 6 inches, bends upon itself 

 horizontally, returns, passes up between the crura of the furcula, bends 

 backwards, and enters the thorax, its diameter in this part of its course being 

 7 twelfths. The inferior larynx is laterally compressed, its last rings united. 

 Appended to the last or semilunar ring on each side is a narrow membrane, 

 terminated by a very slender half ring; the membrane intervening between 

 it and the first bronchial ring is large. The bronchi themselves are very 

 short, compressed at the commencement, enlarged at the middle into a 

 roundish cavity 7^ twelfths in diameter, afterwards cylindrical; their entire 

 length 1|; inches. The lateral or contractor muscles of the trachea are large, 

 and come off at the curve of the furcula, not following the course of the 

 trachea within the sternum, but passing directly across to near the inferior 

 larynx, where they terminate at the distance of 1$ inches. The rings of the 

 trachea are broad and well ossified; there are 148 to the curve, 40 between 

 the lower larynx and its exit from the sternum. The right bronchus has 23, 

 the left 21 rings. 



In the external or subcutaneous cellular tissue of this bird, on the right 

 side, over the thorax, was found a cartilaginous tumour of a roundish form, 

 of which the greatest diameter was H inches. 



Genus IV.— ANAS, Linn. DUCK. 



Bill about the length of the head, somewhat higher than broad at the base, 

 depressed and widened towards the end, rounded at the tip; upper mandible 

 with the dorsal line sloping, and a little concave, the ridge at the base broad 

 and flat, towards the end broadly convex, as are the sides, the edges soft and 

 rather obtuse, the marginal lamellae numerous, oblique; unguis decurved, 

 obovate; nasal groove elliptical, sub-basal, filled by the soft membrane of the 

 bill; lower mandible flattened, slightly recurvate, with the angle very long 

 and narrow, the unguis roundish, the lamellae numerous. Nostrils sub-basal, 

 elliptical, near the ridge. Head of moderate size, oblong, compressed; neck 



