Mr. YARRELL on the Tracheæ of Birds. 383 
Two opportunities having lately occurred to me of examining 
the structure of the Semipalmated Goose (Anas semipalmata) 
of Dr. Latham, who in his Synopsis and General History has 
given a figure of the bird and its trachea, I trust that the anato- 
mical peculiarities I shall be able to exhibit as belonging to this 
bird beyond those already described, will be a sufficient reason 
for adding two representations of parts of both the birds above 
noticed, with some observations on each; premising, that the 
situation of the specimen referred to by Dr. Latham, that of a 
preparation in the collection of Mr. Heaviside, and the addi- 
tional circumstance of two male birds of the same species pre- 
senting two decidedly different conformations of the same organ, 
will sufficiently account for the difference in the two statements. 
Tas. XIII. is an exact representation of the form of the 
trachea in the first male of the two specimens I examined. It 
was situated on the outside of the left pectoral muscle, under 
the skin, and extended the whole length of the side, sufficiently 
raised under the wing that respiration would not be impeded 
when the bird rested with its breast on the ground; the parallel 
tubes being firmly attached both to the muscle and the skin by 
cellular tissue. "These parallel tubes are placed in a more ver- 
tical position in the drawing than when attached to the bird, in 
order to bring the whole of them into view. The additional 
peculiarity of structure to be observed in this bird is the diffe- 
rent formation of one clavicle as compared with the other. The 
clavicle on the right side of the bird is of the usual character ; 
but that on the left is both shorter and wider, having an aperture 
about the middle, the sides diverging, with a projecting point on 
the inner side, to which the tube of the trachea is firmly attached 
about two inches above the bone of divarication. "The trachea 
lying on the left side of the bird, the lower portion of the tube 
in its passage to the lungs crosses the left branch of the fur- 
VOL. XV. 3 D cula 
