PKESIDENTIAL ADDRESS. 73 



there is Comularia australis, a pretty little species with 



creeping rhizome and obconical polyps about half an inch 



« 

 long. The rare Acanthoisis flabellum was obtained alive 



at Maroubra. 



A notable zoophyte is Ceratella fusca, long known from 

 the dried skeleton only, and which was found under rock 

 ledges at the south end of Marouba Bay, in association 

 with Clathrozoon wilsoni. 1 In similar situation occurred 

 Thuiaria sinuosa, Aglaoplienia sinuosa and A. macrocarpa. 



There is a small fish, Iso rhothophilus, which is only 

 seen in the boil of the surf. For this reason, a related 

 species is poetically known to the Japanese as the "Flower 

 of the Wave." 2 



Following the rocks inwards from the surf to the shelter 

 of the harbour, a gradual transition is seen in the compo- 

 sition of the fauna. Though Monodonta and Bembicium 

 persist as far as the rocks go, Helcioniscus, Nerita and 

 other forms vanish. This is partly due to decrease of 

 salinity but chiefly to the presence of mud. The most 

 salient feature is the rise of Ostrea from sporadic occur- 

 rence to the rank of a dominant organism. 



The rock oyster, Ostrea cucullata, is ubiquitous, ranging 

 horizontally from the surf-swept extremity of the ocean 

 reef to the inmost recesses of the mangrove forest; verti- 

 cally from mean tide level to a depth of several fathoms, 

 and in station from rocks and mangrove roots to mud banks 

 and zostera flats. No other constituent of the beach fauna 

 exhibits such plasticity of form, such adaptability to differ- 

 ent positions, such endurance of extremes of temperature 

 or of salinity and from shelter to exposure. In the surf 

 the shell is small, very solid, much crumpled, dentate, and 



1 Spencer, Trans. Boy. Soc. Vict., ii, 1891, p. 123 ; 1892, p. 8, pi. 23. 

 8 Waite, Rec. Austr. Mus., v, 1904, p. 234, pi. 25, fig. 2. 



