1899.] ON THE FORMATION OP COUAL-BREFS. 157 



2. Ou the Formation of the Coral-reefs on the N.W. Coast 

 of Australia. By P. W. Bassett-Smith, R.N., F.Z.S. 



[Eeceived December 15, 1898.] 



Mr. J. Stanley Gardiner has, in his most interesting paper read 

 before the International Zoological Congress at Cambridge last 

 Augnst, again brought the question of the formation of Coral-reefs 

 prominently before the scientific world. The character of the reefs 

 at depths at which corals do not as a rule grow luxuriantly is of 

 prime importance, and as every information of this nature, at first 

 hand from a practical collector and naturalist, is of value if placed 

 ou record, 1 have been induced to bring to light some rather old 

 work done in H.M.S. ' Penguin ' on the North-west coast of 

 Austraha. All the specimens were at the time sent to the British 

 Museum, being presented by the Admiralty ; and, as I have not 

 seen them since, I am not able to give specific or definite names 

 to the specimens, which at the time of collecting it was impossible 

 to do. 



The part worked over consisted of the Holothuria Bank off 

 the Admiralty Grulf, and the Baleine Bank off Roebuck Bay, 

 together with some examinations of the fringiug-reefs of the 

 various islands along the coast. The former is in lat. 13°-13° 30' S., 

 long. 125° 40-126° 20' E., and extends a distance of 60 miles, 

 being at nearest 14- miles from the coast and 100 fi'om the 

 100-fathom hne. The Baleine Bank is in lat. 15° 40' S., long. 

 121° 50' E., and is about 10 miles long. 



The whole area was particularly noticeable for the remarkable 

 abundance of (1) Alcyonarians ; (2) Echinoderms, particularly the 

 most beautiful Asterophytons ; (3) the great quantity of calca- 

 reous Polyzoa of comparatively massive branching character. This 

 region is a great centre of the pearl-shell fishery. 



Mr, Stanley Gardiner, in his paper, states that the building-up 

 is more rapid on the tops of the submarine undulations than in 

 the hollows, from the deposit on them of the downward falling rain 

 of foraminiferal tests, &c. Here I would point out that 

 these strong branching calcareous forms of Polyzoa 

 (including Retiporas) must, in depths of 30 to 60 

 fathoms at least, have a very great building-up power, 

 for time after time the large swabs attached to the dredge-bag 

 would come up perfectly entangled with broken-off branches, as 

 if they had pulled over a little forest of these Polyzoa on a sandy 

 surface, as was shown in my daily dredging report, where they 

 were often described as very abundant and quite " massive." 



In the more elevated portions of the Holothuria Bank, as on the 

 Penguin reef, where there was only 15 fathoms, and on the Bassett- 

 Smith shoal in 9-10 fathoms, the ordinary reef-corals were found 

 {Stylopora, Seriatopora, Astrcea, Goniastrcea, Flesiastnea, Phi/m- 

 astrcea, Turhinaria, 2Ioiitipora, and Pontes), though in shallow 

 . dredgings, 12-20 fathoms, on the Baleine Bank no corals at 



