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 7i twelfths in diameter, afterwards cylindrical ; their entire 
length II 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 li 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 1^ 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 fiat, towards the end broadly convex, as are the sides, the edges soft and 
rather obtuse, the marginal lamellm 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 lamellm numerous. Nostrils sub-basal, 
elliptical, near the ridge. Head of moderate size, oblong, compressed ; neck 
