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MANUAL OF ELEMENTARY ZOOLOGY 



and the other three forwards ; the fifth is wanting. The 

 front or facial portion of the head is drawn out into a beak 

 covered with horny skin. At its base above is a swollen, 

 featherless patch of skin, the cere. The nostrils lie below 

 the cere, the eyes behind it at the sides of the head, and the 



Fig. 288. — A plucked pigeon, seen in ventral view. 



apt., Apteria ; cl., cloacal opening; cr,, cere; ear ; »a., nostril; /A 7 ., pteryla ; 

 / 1 ., thumb ; scl., scales on the foot. 



ear openings below and behind the eyes, covered by feathers. 

 There are three movable eyelids (p. 24), and the drum of 

 the ear is at the bottom of a tube, but there is no ear flap. 

 There is a single cloacal opening, as a transverse slit below 

 the tail, and above the tail is a knob on which opens the 

 oil gland x whose secretion is used in preening the feathers. 



