566 LARIDJ!. 



and tertials tipped or edged with white ; the outer margin 

 of the first primary quill-feather black, the next three 

 tipped with black, the fifth with a black patch near the 

 end, but the extremity white ; tail-coverts and tail-feathers 

 pure white ; chin, throat, breast, and all the under surface 

 of the body and tail pure white ; legs rather short, and 

 dusky in colour, the toes and interdigital membranes also ; 

 the hind toe only a small tubercle without any projecting 

 horny nail or claw, and on this account the species was 

 called tridactylus, three-toed. 



The whole length fifteen inches and a half; from the 

 anterior joint of the wing to the end of the longest quill- 

 feather twelve inches. 



The adult bird in winter has the lower part of the neck 

 behind French grey, like the back ; the occiput, top of the 

 head and the region of the ear-coverts streaked with dusky 

 grey, the other parts as in summer. 



Young birds of the year have the bill black ; the irides 

 dusky, almost black ; upper part of the head white ; the 

 occiput and nape with a few dusky grey patches on a 

 white ground ; the lower part of the neck behind marked 

 by numerous blackish-grey feathers ; back, scapulars, great 

 wing-coverts and secondaries French grey ; point of the 

 wing, and the series of smaller wing-coverts nearly black ; 

 tertials French grey, with a spot of black near the end, the 

 inner broad web varied with white ; tail-coverts and tail- 

 feathers white, the latter black at the end; the middle tail- 

 feathers having the largest portion of black, the outer tail- 

 feather on each side the smallest ; chin, neck, breast, and 

 all the under surface of the body pure white ; under tail- 

 coverts white, tail-feathers white at the base, ending in 

 dark or lead-grey ; legs, toes, and membranes pale brown. 



