IIO The Convolution of the Trachea in the [February, 
the whole the entire conformation of the trachea and sternum in 
canadensis is much simpler than in americana 
Although only the anterior portion of the keel is enlarged for 
the reception of the trachea in canadensis, yet the remainder of 
GENAD 
ve 
ims 
iS 
eS 
TV. 
PLR 
Ci 
FIG. I~GRUS CANADENSIS. 
the keel is not solid bone; but, instead, is composed of two frail 
plates separated by a thin layer of bony meshwork. This light 
_ structure of the posterior part of the keel is more pronounced in 
“some specimens than in others, reaching the greatest development 
yet seen, ina ‘sternum which shows ag the Ka convolution 
s the aen 
