AMERICAN SWAN. 147 



in contact in the keel, are separated anterior to it by a strong ligament, 

 which stretches in aright line across from one limb of the merry-thought 

 to the other, and extends from the outlet from the keel to near the 

 union of the os furcatorium with the clavico-scapular bones. Lateral 

 ligaments also pass from the limbs of the merry-thought to these bones, 

 and form a chamber for the pulmonic portion of the trachea to lie in. 

 The muscles of voice pass from one poi;tion of the tube to the other, 

 and are united to the sternum as in the English species. The bone of 

 divarication is placed perpendicular to the sternum, and is one inch and 

 an eighth from top to bottom, and the sides are so compressed that they 

 are nearly parallel. The space between this bone and the bronchial 

 rings is half an inch, and is occupied by a membranous tube, outside of 

 which extends another membrane from the edge of this bone to a de- 

 licate semi-circular bone on each side, which protects the structure 

 within."" 



Dr Shakpless then states, that Mr Ord and he found the ribs to be 

 ten, and that " the intestines were in every case coiled in seven oblong 

 folds, and two cceca, which were often of different lengths. The dis- 

 tinctive characters of Gygnus ferus, C. Bewickii, and C. Americanus, as 

 given by Mr Yarrell and Dr Sharpless, are then stated to be as fol- 

 lows : 



C.ferus. — Beak black and semi-cylindrical; its hose diaA sides even 

 heyond the nostrils yellow ; body white ; tail with twenty feathers ; feet 

 black. 



C. Bewichii. — Beak black and semi-cylindrical ; hose orange ; body 

 white ; tail with eighteen feathers ; feet black. 



C. Americanus. — Beak black and semi-cylindrical ; sides of the base 

 with a small orange or yellow spot ; body white ; tail with twenty fea 

 thers ; feet black. 



