INTRODUCTION. 
Genus Gelochelidon, Brehm. 
It would be strange if this form did not exist in Australia, when all the other European genera of Terns are 
found there ; still I have no other evidence of such being the case, than that of a specimen in the collection of 
King's College, London, which is said to be from Van Diemen's Land, and to which in the year 1837 I gave the 
name of Sterna macrotarsa. 
568. Gelochelidon macrotarsus, Gould. 
Sterna macrotarsa, Gould in Proc. of Zool. Soc, Part V. p. 26 ; and in Syn. Birds of Australia, Part II. 
Crown of the head and bach of the neck black ; all the upper surface and primaries light silvery-grey ; 
remainder of the plumage white ; bill and feet black. 
As I did not meet with this bird myself either in Van Diemen's Land or in any other of the Australian regions, 
I have not figured it. 
Genus Gygis, Wagi. 
One species of this Polynesian genus of Terns is found in Australia. 
569. Gygis Candida Vol. VII. PI. 30. 
Genus Hydrochelidon, Boie. 
The value of minor genera or subgenera, as naturalists may choose to designate them, is much strengthened, 
when species, which have been assigned to either of them from countries so distant from each other as Australia 
and Europe, are found to possess similar habits, but differing from those of the other members of the family. Thus 
the members of the present little group inhabit the inland waters and marshes of both countries ; make their nests 
among" the"rushes, and lay thickly -marked eggs, in both of Avhich particulars they differ from the other Terns ; the 
generality of which deposit their eggs on the shingles of the sea-shore, while others, the Gygis Candida for instance, 
lay their single egg on the horizontal branch of a tree, so totally unprotected, that how it is retained in its position 
during windy weather is a perfect mystery ; others again, such as the Noddies, bring together large masses of 
sea-weed, which they either pile upon the swinging branch of a Mangrove or on the jutting point of a rock. All 
these facts should be studied by ornithologists before they discard subgenera proposed by their fellow-labourers, 
and replace the species they may have so divided in the genera of the older writers, who must necessarily have 
known less of the subject; for 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, Gom/(^ . . . ... . . . . . . Vol. VII. PI. 31. 
A fine marsh Tern differing from its European prototypes H. nigra, H. leucoptera, and H. leucopareia. 
Genus Onychoprion, Wagl. 
Of this form two species frequent the Austrahan seas. 
571. Onychoprion faliginosus . . . . . . . • • • • • Vol. VII. PI. 32. 
Although I have figured one of the two Australian birds of this genus under the above appeUation, rather 
than run the risk of unnecessarily adding to the number of species, I have no doubt it will prove to be distinct 
from the American bird. 
