448 ■ Mr. Yarrell on a new Species of Wild Swan. 



being defended on each outer side by a distinct membrane, 

 attached to the whole edge of the bone of divarication ; and 

 posteriorly to a slender semicircular bone on each side, by 

 which it is supported. The muscles of voice with which this 

 bird is provided, pass down, as usual, one on each side of the 

 trachea till the tube is about to enter the cavity in the keel, 

 they then quit that part of the tube to be attached to the 

 ascending portion of the curve, which they follow, ultimately 

 branching off a little short of the bone of divarication to be in- 

 serted upon each side of the sternum (Tab. XXIV. Fig. 1. 

 & 2. Letters d. d. d). 



The stomach, a true gizzard, is only half as large as the same 

 part in the Mute Swan, and one-third less than that of the 

 Hooper ; the intestinal canal is uniform in calibre, coiled up in 

 seven oblong folds, measuring from the pylorus to the end of the 

 rectum ten feet two inches, with two caeca of ten inches each. 



In their general external appearance, the Hooper and this 

 new species are similar ; and that they have been so long con- 

 founded together is probably owing to the circumstance that 

 the Hooper, when first gaining its white plumage, is but little 

 larger than the adult bird of the new one. The head of the 

 new species is however shorter, and the elevation of the cra- 

 nium greater, in proportion to the size of the head ; the beak 

 narrow at the middle, and dilated towards the point. The 

 wings when closed do not extend quite so far beyond the roots 

 of the tail feathers ; the tail itself is somewhat more cuneiform ; 

 and the toes appear shorter in proportion to the length of the 

 tarsi. In the Hooper, the sides of the beak are parallel, the 

 bright yellow colour at the base of the upper mandible ex- 

 tends along each outside edge even beyond the line of the nos- 

 trils, and occupies a much larger space comparatively than in 

 the new species. But the following relative measurements of 



the 



