JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 19 



Unguis. The nail on the end of the upper mandible. Very pro- 

 nounced in some families of Water Birds. (Ducks, Pelicans, and 

 Petrels.) 



Mandibles. Some authors use the word maxilla for the upper 

 half of the bill, and mandible, for the lower. I prefer, however, to 

 describe the two halves of the bill as upper and lower mandible. 



