482 NATATORES. LARUS. 
black, with a slight tinge of red. Tarsi one inch and 
three quarters long. 
Summer In summer, the forehead, crown, and back part of the 
ee neck are deep black. In other respects there is no 
striking difference between that and the winter plumage. 
Genus LARUS, Zinn. GULL. 
GENERIC CHARACTERS. 
Bit of mean length, strong, strait, cultrated ; the upper 
mandible having the tip incurved ; symphasis of the lower 
mandible strongly angulated, and ascending from thence to 
the point. Nostrils placed in the middle of the bill, lateral, 
oblong, narrow, and pervious. ‘Tongue pointed, with the 
extreme tip cloven. Wings long, acuminate. Tail even, or 
slightly forked. 
Legs placed near the centre or equilibrium of the body, of 
mean length and strength, with the lower part of the tibize 
naked. Feet of four toes, three before and one behind ; the 
three front toes united by a membrane ; the hind one short 
and free, articulated upon the back part of the tarsus. Nails 
slightly falcate. Tarsi and upper part of the toes scutel- 
lated. 
The passage from the Terns to the larger and more typi- 
cal Gulls, is effected by certain small species of the latter 
genus, possessing a less robust bill, and slightly forked tail. 
In their changes of plumage also, they shew their connexion 
with the former birds, by the head becoming entirely or partly 
of a dark colour, as the season of reproduction approaches, and 
being more or less white during the rest of the year. In the 
larger Gulls the reverse takes place, the head and neck being 
of an unsullied white during the summer, and in winter being 
