SHY MOLLYMAWK. 
These three forms at present constitute the species which appears to 
absolutely merit the name given to it by Gould. 
The nomenclature to be used will therefore be :■ — 
Thakbssogeron cautus cautus Gould ; 
East Australian seas (breeding, Bass Strait). 
Thalassogeron cautus salvini Bothschild ; 
New Zealand seas (breeding. Bounty Island). 
Thalassogeron cautus layardi Salvin ; Cape seas (breeding). 
In the E7nu, Vol. VII., p. 56, 1907, there is the following note regarding 
this bird and its relationship with Th. salvini, by Mr. D. Le Souef : “ Sir W. L. 
BuUer quotes from the Hon. W. Bothschild, when writing on the Diojnedea cauta, 
in which Mr. Bothschild states that he will need a lot of evidence before he 
can admit that the so-called Thalassogeron cautus is a female of T. salvini. I 
quite agree with him, and do not for a moment consider that the two birds 
named are identical, judging by the illustrations of the head of T. salvini in 
BuUer’s work. Perhaps it would be a help if I gave a description of one of the 
birds I procured at Albatross Island, in Bass Strait, where they were nesting, 
and which we consider is T. cautus of Gould : Crown, breast, and neck pure 
white, the back of the neck gradually changing into greyish black on the lower 
back ; a dark gre 3 dsh-black line goes from the upper part of the bill to the eye 
and thence continued as a much paler broad patch below and behind the eye, 
running down the side of the neck for from 4 to 5 inches and practically meeting 
at the back of the crown and forming a conspicuous white cap. In the female 
the delicate grey colour on the side of the head is much paler and fades away 
to within a short distance of the eye and does not meet at the back. The 
rump and upper and lower tail coverts white, the centre under tail coverts 
slightly tinged with grey ; the tail is grey and lighter below, with the outer 
webs paler, the shafts are white ; the upper wing coverts are greyish-black, 
like in the other species ; the primaries are grey on the outer web and white 
on the inner, the white changing into grey towards the tip ; the shafts are 
white above and dark below ; the under surface of the body and the under 
wing coverts are white ; the beak is greyish horn colour, darker below, and the 
point horn colour. Total length 40, culmen 6, wing 22, tail 9, tarsus 
3.25 inches.” 
The exact differences between Th. c. cautus and Th. c. salvini are better 
understood when it is fully conceded that they are only subspecifically 
separable. The latter can always be recognised by means of the bill, as the 
figure given by BuUer shows. 
VOL. II. 
293 
