502 - PEOCELLARIIDJi; THALASSOGBEON 



Description. Adult. — Head and neck all round slaty-grey (perhaps 

 becoming white in very old specimens) darker in the centre of 

 the back and blackish brown on the wings ; tail like the back with 

 white shafts to the feathers ; in front and above the eye a dark 

 patch ; rump, upper tail-coverts and lower surface from the chest 

 to the under tail-coverts white, under wing-coverts white, dark 

 brown towards the edge of the wing. Bill with the culminicorn, 

 which is rounded behind and separated behind the nostrils from 

 the latericorn by a black membrane, yellow, front edge of the apicorn 

 red, lower half of the latericorn of the lower mandible yellow, rest 

 of the bill blackish horn ; legs and feet fleshy grey. 



Fig. 154. — Left foot of Thalasaogeron clilororhxjnclms. x i 



Length about 32 ; wing 18-5 ; tail 7-0 ; culmen 5-25 ; tarsus 3-0 ; 

 middle toe 4-1. Young birds are browner and have the head leaden 

 grey ; the bill is black throughout with a little yellow at the tip. 



Distribution. — This Mollymawk, distinguished by having both the 

 upper and lower ridge of the bill yellow, is found throughout the 

 Southern Ocean, ranging chiefly between the 30th and 50th parallels 

 of south latitude. It does not appear to have been met with so far 

 south as the Antarctic Ice Pack, but has been known to wander as 

 far north as Panama in Central America on the Pacific side. 



