VERTEBRATA: AVES. 



60 5 



The Darters or Snake-birds (Plotus] are somewhat aberrant 

 members of this group, characterised by their elongated necks 

 and long pointed bills. They occur in America, Africa, and 

 Australia, and catch fish by suddenly darting upon them from 

 above. 



Fam. 4. Lamellirostres. The last family of the Natatores 

 is that of the Lamellirostres, including the Ducks, Geese, 

 Swans, and Flamingoes, and characterised by the form of 

 the beak (figs. 332 and 334), which is flattened in form and 



Fig. 334. A, Head of the Grey Lag Goose ; B, Foot of the domestic Goose. 



covered with a soft skin. The edges of the bill are further 

 furnished with a series of transverse plates or lamellae, which 

 form a kind of fringe or " strainer," by means of which these 

 birds sift the mud in which they habitually seek their food. 

 The bill is richly supplied with filaments of the fifth nerve, and 

 doubtless serves as an efficient organ of touch. The feet are 

 furnished with four toes, of which three are turned forwards, 

 and are webbed, whilst the fourth is turned backwards, and is 

 free. The trachea in the males is often enlarged or twisted in 

 its lower part, and co-operates in the production of the pecu- 

 liar clanging note of most of these birds. The body is heavy, 

 and the wings only moderately developed. 



The groups of the Ducks (Anatidcz), Geese (Anserince), and 

 Swans (Cygnidcz), are too familiar to require much special notice. 

 The Anatidce, or true Ducks, have the hallux furnished with a 



