808 " THETIS " SCIENTIFIC RESULTS. 



the Hydroid fauna of South-east Australia, from a collection 

 limited to about half the known species in that area, the general 

 facts are clear. That, although an unusually large proportion of 

 this fauna is peculiar to Australia, there are also many species 

 common to it and other oceanic regions. These do not appear to 

 bear out the statement of W. M. Bale^ that " the Hydroida of 

 the South-eastern province have more affinity with those of New 

 Zealand than with these of any other part of the globe." For, 

 of the twenty-two species concerned, thirteen have been found in 

 the Indian Ocean, thirteen in the Atlantic, and ten in the 

 Pacific, while only six occur in the neighbourhood of New 

 Zealand. Miss L. R. Thornely has, however, justly drawn 

 attention to the similarity which exists between the Hydroid 

 fauna of Indian seas and that of Australia,'^ for it is probable 

 the latter is more closely allied to the former than to any other. 



As regards the local distribution : — The average number of 

 species obtained at the productive Stations is slightly under five, 

 the Stations at which larger numbers were obtained being 36 

 (8 spp.), 44 (13 spp.), 48 (9 spp.), 54 (9 spp.), 57 (6 spp.). Exami- 

 nation of the provenance of the specimens would lead one to 

 suppose that the Hydroid fauna was most abundant in the 

 coastal region which lies between Port Jackson and Bulgo (to 

 the south of Port Hacking), but this supposition is discounted 

 by the fact that it was precisely in this area that the collecting 

 of the " Thetis " was most intense. 



Besides the Hydroid Zoophytes proper, there has been included 

 in this report Stylaster eximius, the only calcareous Hydrozoon 

 received by me. It has not hitherto been recorded from Australia. 



I cannot conclude this introduction to the description of a 

 highly interesting Australian collection of Hydrozoa, without 

 paying tributes to the unrivalled work accomplished for Australian 

 Zoophytology by Mr. W. M. Bale in his admirable " Catalogue," 

 published by the Trustees of the Australian Museum, supple- 

 mented by his later papers ; and to the painstaking studies of 

 Dr. Armand Billard, whose examinations of type specimens have 

 done much to free the literature of Hydroids from mystifying 

 synonyms. 



Finally, I would express my thanks to the Trustees of the 

 Australian Museum for entrusting to me, for examination, the 

 collection brought together by the "Thetis." 



18th January, 1911. 



1 Bale— Cat. Austr. Hydroid Zoophytes, Sydney, 1884, p. 32. 



2 Thornely — in Herdman, Rep. Ceylon Pearl Oyster Fisheries, Part ii.,, 

 Suppl. Rep. viii. — Hydroida, p. 107. 



