272 



ANAT1D;E. 



the upper mandible, by the end of January, but it more fre- 

 quently begins at a later period, namely, in March. 



The trachea of this species is singular in its form, diifering 

 from the character of those of the Ducks in general, and 

 bearing some resemblance to those of the Mergansers, both 

 in the tube and in the labyrinth. The length is about nine 

 inches, the diameter of the upper half of the tube equal in 

 size and small ; at the commencement of the second half, the 

 tube is dilated to four times the previous size, and the rings 

 are so arranged as to lay flat upon each other. The last, or 

 fourth, portion again contracts till it ends in the labyrinth, 

 of Avhich the vignette below represents the surface nearest 

 the back of the bird. The bronchial tubes are observed to 

 be unequal in length, to compensate for the obliquity of the 

 inferior surface of the labyrinth, which, as usual, is made up 

 partly of bone and partly of membrane. 



