204 



FIRST LESSONS IN ZOOLOGY. 



men ; they connect with the ends of some of the air-tubes, 

 and also with the hollows of the bones, so that the bird's 

 body is lightened and buoyed up by air. 



FIG. 211. Head of a bird, ce, cere; n, nostril; u, upper mandible; t, tomia; d, 

 tooth; e, culmen; p, tips of mandibles; i, under mandible; yo, gonys; </, gape. 



Another feature in which birds differ is in the shape of 

 the bill (Figs. 212, 213, 214). The jaws are toothless and 



FIG. 212. Cockatoo's Beak,the 

 dotted line showing the posi- 

 tion of the upper bill when 

 raised. 



FIG. 213. Beak of the Shoe- 

 bill, Balceniceps rex. Africa. 



FIG. 214. Heteralocha acutirostris. 

 From New Zealand. .-I, male; B, 

 female, with its reniarkably long, 

 curved beak, enabling it to search 

 for insects in rotted trees. 



encased in horn, and the form of the bill is closely related 

 to the kind of food and the manner in which it is taken. 

 The bill in its simplest form is pointed and conical ; the 



