COMMON SHELLDRAKE. 241 



gangers, forming together the large, the valuable, and in- 

 teresting family of the Anatidse ; and I may here refer 

 particularly to that organ as found in the Shieldrake, 

 which is so entirely distinguished from that of any other 

 species, as at once and alone to afford, as far as I have yet 

 seen, a decided specific character. The trachea, or wind- 

 pipe, in the Shieldrake is about ten inches long, nearly 

 uniform in size throughout its length, except towards the 

 bottom, where, for about one inch, it is much smaller. On 

 each side of the bone of divarication, forming the bottom 

 of the tube, there is a globular, hollow, bony protuberance, 

 that on one side being as large again as the one on the 

 other. The bone is thin, and so flexible when in its moist 

 and natural state as readily to become indented on pres- 

 sure. The representation given below is only a little 

 smaller than the natural size. The tube below each en- 

 largement, going off, one to each lobe of the lungs, presents 

 nothing remarkable. 



