454 Mr. Yarrell on a new Species of Wild Swan. 



Fig. 2. Upper surface of the sternum of an older bird, showing 

 the loop of the trachea occupying one side of the ca- 

 vity only. Part of the slender plate of bone being 

 cut away. 

 3. Upper surface of the sternum of an adult bird, the cavity 

 wholly occupied by the loop of the trachea. Part of 

 the plate of bone being also cut away. 

 All the representations are one-fourth less than the na- 

 tural size. 



