84 American Wild Swan. 
pt. II. in which he divides the English wild swan into two species, and 
describes them both minutely, giving us an opportunity before want- 
ed, of instituting a comparison between them, and our own. 
The Hooper (Cyenus ferus) is five feet from the point of the bill 
to the end of the tail—seven feet ten inches between the tips of the 
wings, and weighs twenty four pounds. From the point of the beak 
to the edge of the forehead, four inches and three eighths, and from 
the same point to the occiput, seven inches and one fourth—the sides 
of the bill parallel—the bright yellow color at the base of the up- 
per mandible extends along each outside edge even beyond the line 
of the nostrils—tail twenty feathers. It is the internal structure 
that marks so particularly the character of the Hooper. This pecu- 
liar arrangement has been long known to exist, but has never before 
been so carefully described as to enable naturalists to found species 
on its variations. The trachea or windpipe which is of equal diame- 
ter throughout, enters a cavity in the keel of the sternum or breast- 
bone, formed by a separation of its plates; and passing back nearly 
to the posterior extremity of the keel, folds upon itself, always retain- 
ing the vertical position in its doubling, and returns out at the same 
orifice it entered the keel, and winding round the merry-thought 
(os furcatorium) takes the regular route to the lungs. 
In the oldest Hooper, this cavity never extended in the slightest 
degree farther back than'the keel, and the fold of the windpipe 
never left the vertical position at any age. ‘The bone of divarication 
or larynx is compressed, and the membrane between it and the bron- 
chial tubes is unprovided with an arrangement to protect it, as it is in 
his other species. ‘The bronchial tubes are very long. The differ- 
ence in the admeasurements between the Hooper and his second spe- 
cies C. Bewickn, will be given, when I mention our own swan. I 
will now point out the distinguishing marks of the Bewick. 
The beak is black at the point, and orange-yellow at the base; 
this last color appears first on the sides of the upper mandible, and 
afterwards covers the upper surface in front of the forehead to the 
extent of three fourths of an inch, receding from thence by a con- 
vex line to the lower edge of the mandible at the gape—the irides 
orange-yellow—the beak narrow at the middle, and dilated towards 
the point. 
“The trachea enters a cavity in the keel of the sternum as in 
the Hooper, and having traversed the whole length of the keel, the 
tube then gradually incliniag upwards and outwards, passes mto a 
cavity in the body of the sternum posterior to the keel, produced by 
