SURF DUCK. 167 
and presently enlarges to form the inferior larynx, which is large, os- 
sified, but symmetrical. In this space there are 6 distinct rings, and 
10 united. The entire length of the trachea is 73 inches, its rings are 
all osseous and strong. The contractor muscles are very strong, pass 
along the sides of the lower dilatation, on which are given off the cleido- 
tracheals, then continue to the commencement of the inferior larynx, 
where the sterno-tracheals come off. The bronchial half-rings 25, un- 
ossified. 
The cavity of the nose is very large, being 2 inches long, 3 inch 
in diameter at the lower part, continued narrow in front over the di- 
latation causing the external protuberance of the base of the bill. The 
olfactory nerves are of moderate size; the maxillary branches of the 
fifth pair very large. 
