ORDER GAVI^E. 5 



plumage changes. Many species, however, appear to be capable of breeding before 

 they have assumed their fully mature plumage. 



The Larince are divided into seven genera, among which the fifty-four 

 recognized species are relegated : 



i. Xema, containing two species (circumpolar in habitat in summer, but 

 ranging beyond the tropics in winter), with long wings, forked tail, and the hind 

 toe free and very small. One of the species is recorded from Britain. 



2. Rhodostdhia, in which only one a circumpolar species is included, at 

 once characterized by its wedge-shaped tail, the two central feathers being nearly 

 two inches longer than the others, a character xmique among the Gulls. 



3. Larus, embracing, according to Mr. Saunders' latest investigation of the 

 group, forty-four species (a dozen of them being either resident in, or visitors to 

 the British Isles), having the tail square ; the bill, with linear nostrils, three times 

 as long as it is deep ; the hind toe free and well developed, and the lower third 

 of the leg bare. In some species the mature birds assume a dark head in the 

 breeding season ; as a rule, however, dark feathers, or a speckled plumage, indicate 

 immaturity. 



4. Gabianus, containing a single Australian species, resembling in outward 

 appearance the Great Black-backed Gull, with a stout and compressed bill, of 

 which the length is less than twice the depth. 



5. Leucophceus, containing one species, inhabiting southern South America 

 and the Antarctic Islands, with the hind toe joined to the inner by a rugose 

 membrane ; the feet coarse, strong, and their webs considerably indented ; the bill 

 very short and obtuse (Saunders). 



6. Rissa, the KiTTiWAKES, numbering two species, with an arctic summer 

 habitat, extending in winter into sub-tropical latitudes ; having the hind toe very 

 rudimentary, or absent, though occasionally not ill developed ; the tarsus very short 

 compared with the middle toe and claw ; the bill peculiarly curved ; the tail slightly 

 forked ; the plumage of the immature bird quite unlike that of the adult, or of the 

 young of other species of the subfamily ; they nest invariably on precipitous rocks. 



7. Pagophila, containing a single representative, the IVORY GULL, with the 

 bill short and stout ; the feet coarse, rough with serrated membranes, much 

 excised webs and strong curved claws (Saunders) ; the hind toe joined to the 

 inner toe on the inside of the foot by a serrated membrane. The Ivory Gull has 

 a circumpolar habitat. 



The true Gulls (Laritice) have the bill with its npper mandible longer than, 

 and bent down over the tip of, the lower; the tail square, rarely forked or 

 wedge-shaped. 



