52 A MANUAL OF THE BIRDS OF AUSTRALIA. 



Immature. When the young flies it has a dark grey head which extends on 

 to the throat ; the ocular patch distinctly bla-ckish ; 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 light 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 bill, have the head white and the back 

 of the neck inclining to white. 



Nest, Egg, and Breeding-season. Unknown. 



Distribution and forms. Sub-antarctic as far as is known. Four forms can be 

 recorded, but more material is necessary before finality can be suggested. These 

 are : T. c. chrysostoma Forster, from Cape Seas (of which D. culminata Gould may 

 be a synonym) ; T. c. mathewsi (Rothschild) from Campbell Island, New Zealand, 

 as having the cheeks and throat pure white, and top of head white, not grey ; back 

 browner ; T. c. harterti Mathews, from South Indian Ocean (Kei^uelen Island 

 breeding) in its deeper, heavier bill, coloration as in preceding ; T. c. alexanderi 

 Mathews, from West Australian seas, with smaller and paler bill. 



40. Thalassarche chlororhynchus. YELLOW- NOSED MOLLYMAWK. 



[Diomedfa chlororhynchos Gmelin, Syst. Nat., Vol. I., pt. 11., p. 568, April 20th, 1789 : Cape 

 Seas. Extra-limital.] 



Gould, Vol. VII., pi. 42 (pt. xv.), June 1st, 1844. Mathews, Vol. II., pt. 3. pis. 98 and 99, 

 Sept. 20th, 1912. 



Thalassogeron carteri Rothschild, Bull. Brit. Ornith. Club, Vol. XIV., p. 6, Oct. 30th, 1903 : 



Point Cloates, mid-West Australia. 



Diomedea bassi Mathews, Nov. Zool., Vol. XVIII., p. 206, Jan. 31st, 1912: " New South 



Wales." 



DISTRIBUTION. Southern Australian Seas. 



Adult male. Back, scapulars and wings slaty-brown, tail-feathers hoary -grey, 

 lesser, median, and greater wing-coverts dark brown with white bases, like the 

 bastard-wing and primary-coverts ; primary-quills black on the outer webs, hoary- 

 grey on the inner ones, with white shafts at the basal portion ; secondaries dark 

 brown, white on the inner webs ; some of the feathers of the olecranal region dark 

 brown while others are white with brown tips ; humeral feathers also dark brown ; 

 rump and upper tail -coverts white ; a patch on each side of the breast grey, like the 

 back ; a pale grey line in front and over the eye ; head and neck all round, mantle 

 and entire under-surface white, as also the axiUaries ; under wing-coverts white, 

 those around the margin dark brown ; bill black, culmen yellow, passing into orange 

 at the tip ; a line at the base of the mandible yellow ; legs flesh colour. Total 

 length 710 mm, ; culmen 118, wing 464, tail 190, tarsus 75. 



Adult female. Similar to the adult male. 



Immature. Agrees in general coloration with the adult, but differs from that 

 in the colour of the bill, which is in this wholly black (due to immaturity) ; irides 

 black ; feet and legs yellowish -white. Culmen (exp.) 1 14 mm. long, depth at base 36, 

 wing 462, tail 165, tarsus 75. (T. carteri Rothsch.) 



Nestling, Eggs, and Nesting -place. Unknown. 



Distribution and forms. Apparently Sub-antarctic but not well known. Races 

 not yet determined. Thus the West Australian bird was named from an immature 

 specimen and the Tristan d'Acunha bird described as D. eximia Verrill, owing to a 

 misunderstanding of the species. When breeding places are discovered forms may 

 be accurately circumscribed. 



