446 Mr. YARRELL on a new Species of Wild Swan. 
numerous. More than fifty were counted in one flock at Wit- 
tlesey-mere. Among a considerable number which have been 
forwarded to the London markets for sale, I have been most 
unexpectedly fortunate in securing five examples of this new 
species, of different ages; and possessing thus a series of gra- 
dations in structure, which it is the object of this memoir to 
describe, I have no doubt of proving them to belong to a spe- 
cies entirely distinct, though hitherto confounded with our more 
common winter visitor the Hooper ; ornithologists having as yet 
admitted but one species of Wild Swan in their systematic cata- 
logues of European Dirds. : 
In size the new species is one-third emiáller than the Hooper 
at the same age. The plumage is first grey, afterwards white, 
tinged with rust-colour over the head and on the under surface 
of the belly, and ultimately pure white. The beak is black at 
the point, and orange-yellow at the base; this last colour ap- 
pears first on the sides of the upper mandible, and afterwards 
covers the upper surface in front of the forehead, to the extent 
of three quarters of an inch, receding from thence by a convex 
line to the lower edge of the mandible at the gape; the nostrils 
are oblong and open; the irides orange-yellow ; the wings 
have the second and third primaries the longest and equal, the 
first and fourth half an inch shorter than the second and third, 
and also equal; the tail consists of eighteen feathers, gra- 
duated, cuneiform ; the legs, toes, and claws, black. 
In anatomical structure the new species differs much more 
decidedly from the Hooper than in its external characters. "l'he 
principal difference is in the trachea, which forms one of the best 
distinctions in the separation of nearly allied species throughout 
this numerous family. | 
The tube of the wind-pipe is of equal diameter throughout, 
and descending in front of the neck enters the keel of the ster- 
num, which is hollow as in the Hooper, traversing its whole 
| length. 
