NATATORES. 505 



legs, and amongst them are almost the only Natatorial Birds 

 which ever perch upon trees. 



The Pelicans (Pdicamdx) are large birds, which subsist on 

 fish, and are found in Europe, Asia, Africa, and the New 

 World. They sometimes measure as much as from ten to fif- 

 teen feet between the tips of the wings, and most of the bones 

 are pneumatic, so that the skeleton is extremely light. The 

 lower mandible is composed of two flexible branches which 

 serve for the support of a large "gular" pouch, formed by the 

 loose unfeathered skin of the neck. The bill is long and 

 straight, and the upper mandible is strongly hooked at the tip. 

 The fish captured by the bird -are temporarily deposited in this 

 pouch, and the parent birds feed their young out of it. 



In the Cormorants (Phalacr.ocorax) there is no pouch be- 

 neath the lower mandible, but the skin of the throat is very 

 lax and distensible ; the nail of the middle toe is serrated. 

 They are widely distributed over the world, one species being 

 very abundant in many parts of Europe. The Gannets 

 (Sula) have a compressed bill, the margins of which are finely 

 crenate or toothed. They occur abundantly on many parts of 

 the coasts of northern Europe, one of the most noted of their 

 stations being the Bass Rock at the mouth of the Frith of 

 Forth. Another species (Sula variegata) is of greater import- 

 ance to man, as being one of the birds from the accumulated 

 droppings of which guano is derived. The Frigate-birds 

 (Tachypetes) are chiefly remarkable for their extraordinary 

 powers of flight, conditioned by their enormously long and 

 powerful wings and long forked tail. They occur on the coasts 

 of tropical America, and are often found at immense distances 

 from any land. The Tropic-birds {Phaeton) inhabit inter- 

 tropical regions, and are found far out at sea. They have 

 short feeble feet, and long pointed wings. 



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. Lamdlirostres. 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 (fig. 211, 217), which is flattened in form and 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 



