THE BIRDS OF AUSTRALIA. 
When the young flies it has a dark grey head which extends on to the throat ; 
the ocular patch distinctly blackish ; the grey is a dirty -brown grey, while the 
bill is practically all black, but the lower edges of the under mandible show pale 
brownish. The grey head and neck lose their brownish tinge while the culmen 
takes on a hght yellowish-brown shade, the strip on the lower edges of the 
lower mandible becoming paler. The fully-adult has a beautiful pearl-grey 
head, neck and throat, while the culmen is pale clear yellow and the lower edge 
of the lower mandible is also clear light horn or yellowish. 
Some birds, however, in the change, as shown by the coloration of the 
biU, have the head white and the back of the neck inclining to white. I cannot 
reconcile these with the pure grey-headed adults, and it is noteworthy that 
such come from different localities. It will be noted that Gould described his 
bird as having the “ crown of the head white ” and all “ the under surface 
white,” so that all is not yet known regarding this species. 
I would recognise the following subspecies : — 
Thalassogeron cTirysostoma dirysostoma Forster ; Cape seas (breeding). 
Thalassogeron dirysostoma harterti, subsp. n.. Type no. 5579 ; 
South Indian Ocean (Kerguelen Island breeding). 
Differs from Th. c. dirysostoma in its deeper, heavier bill, and agreeing in 
coloration of head and neck with Th. c. mathewsi Rothschild. 
Thalassogeron dirysostoina cuhninata Gould ; Austrahan seas (breeding). 
Thalassogeron ehrysostoma 'tnathewsi Rothschild ; 
New Zealand seas (Campbell Island breeding). 
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