113 
wherever a difference occurs in the habits of the members of any 
great family a variation more or less marked will be found in their 
structure. So far as my own observations go, and they have not 
been few, if I have read the great book of nature aright, the genera, 
instead of being reduced, might with propriety be multiplied without 
the risk of our being burthened with a genus for every species, as 
some writers affect to fear would then be the case. 
570. Hydrochelidon fluviatilis, Gould . . . Yol. VII. PL 31. 
A fine marsh Tern differing from its European prototypes H. nigra, 
FL leucoptera , and H. leucopareia. 
Genus Onychoprion. 
Of this form two species frequent the Australian seas. 
571. Onychoprion fuliginosus Yol. VII. PL 32. 
Although I have figured one of the two Australian birds of this 
genus under the above appellation, rather than run the risk of un- 
necessarily adding to the number of species, I have no doubt it will 
prove to be distinct from the American bird. 
Found breeding in prodigious numbers on Raine’s Islet and 
Bramble Key in May and June, associated with Noddies (Anoiis 
stolidus). The Sooty Tern deposits its solitary egg in a slight ex- 
cavation in the sand without lining of any kind. The egg varies con- 
siderably in its markings. After the party employed in building the 
beacon on Raine’s Islet had been on shore about ten days, and the 
Terns had had their nests robbed repeatedly, the birds collected into 
two or three large flocks and laid their eggs in company, shifting 
their quarters repeatedly on finding themselves continually molested ; 
for new-laid eggs were much in request among people who had 
for some time been living upon ship’s fare. By sitting down and 
keeping quiet I have seen the poor birds dropping their eggs within 
two yards of where I sat, apparently glad to get rid of their burthen 
at all hazards. During the month of June 1844 about 1500 dozen 
of eggs were procured by the party upon the island. About 
the 20th of June nearly one half of the young birds (hatched 
twenty-five or thirty days previously) were able to fly, and many 
were quite strong upon the wing. Great numbers of young birds 
unable to fly were killed for the pot ; — in one mess of twenty-two 
men the average number consumed daily in June was fifty, and sup- 
posing the convicts (twenty in number) to have consumed as many, 
3O00 young birds must have been killed in one month ; yet I could 
observe no sensible diminution of the number of young, a circum- 
stance which will give the reader some idea of the vast numbers of 
birds of this species congregated on a mere vegetated sand-bank 
like Raine’s Islet. 
572. Onychoprion Panaya Yol. VII. PL 33. 
Genus Anous. 
Unlike other Terns which frequent the sea-shores and rivers, the 
Noddies inhabit the wide ocean, far remote from land, and which, 
i 
