American Wild Swan. 85 
the separation of the parallel horizontal plates of bone forming the 
broad, flattened, posterior portion of the breast-bone, and producing a 
convex protuberance on the inner surface. 
“The tube also changing its position from vertical to horizontal, and 
reaching within half an inch of the posterior edge, is reflected back 
after making a considerable curve, till it once more reaches the keel, 
after traversing which, in a line immediately over the first portion of 
the tube, it passes out and reaches the lungs asin the Hooper. This 
was the state of developement in the most perfect bird. 
“The degree next in order, differs in having the horizontal loop of 
the trachea confined to one side only of the cavity in the body of the 
sternum, both sides of which cavity, are at this time formed, but the 
loop of the tube is not yet sufficiently elongated to occupy the whole 
space. 
“The third in order, being that of a still younger bird, possesses 
only the vertical insertion of the fold of the trachea, yet, even in 
this specimen, the cavity in the posterior portion of the sternum 
already exists toa considerable extent. The bronchie are very 
short, and the flexible, delicate membrane that intervenes between the 
bone of divarication and the bronchial rings, is quite elongated, and de- 
fended on each side by a distinct membrane attached to the whole 
edge of the bone of divarication, and posteriorly, to a slender semicir- 
cular bone on each side, by which it is supported. The muscles of 
voice pass down as in the Hooper, one on each side of the trachea, till 
the tube is about to enter the keel, they then quit that part of the tube 
and pass to the ascending portion that has just issued from the keel, 
which they follow, ultimately branching off a little short of the bone of 
divarication to be inserted on each side of the sternum. 
“The stomach, a true gizzard, is one third less than that of the 
Hooper—the intestinal canal is uniform in calibre and coiled up in 
seven oblong folds with two ceca. 
«As in the Hooper, the plumage is first grey, afterwards white 
tinged with rust color over the head and on the under surface of the 
belly, and ultimately pure white. The tail has but eighteen feathers.” 
I will now describe a mature specimen of the American swan, 
and afterwards give such variations as youth may produce. 
From its size, and the toughness of the joints and flesh, and the 
perfect absence of every mark of juvenility, I have no doubt this 
bird possessed every perfection of developement. _ It will be observ- 
ed, that the dimensions and characters of the specimen, preserve, 
in a great degree, a middle course between the English species. 
