PRESIDENTIAL ADDRESS. 77 



that underlie a continuous crust of Galeolaria ccespitosa, Lamk. 

 This is a dominant form in the mid-tidal horizon of the ocean 

 rock beach. Masses of the annelid tubes have built a cornice over- 

 hanging the pool, and in rolls, knobs, and pillows it chokes the 

 fissure in the foreground. In fluent outline this growth recalls 

 that of a coral reef in the surf. A few patches of stunted Hormosira 

 occur on the left. 



Plate V, Fig. 10. 



A colony of limpets, Helcioniscus variegatus, perched on a smooth 

 bare sheet of rock, exposed to heavy surf at Long Reef, near mean 

 tide level. These have neither weed nor rock to shelter them, but 

 depend for safety on resistant form. 



Plate VI. 



The beach bank of Dee why Lagoon seen at low water; on the 

 horizon is Long Reef. The outflow in the middle distance is now 

 closed by a sand-beach built across by the ocean surf. Through 

 this a stream in flood time will break a channel. The main body 

 of the lagoon extends to the left for a considerable distance. 



Photographed by Mr. J. Degotardi and published by the kind 

 permission of the Director General of Public Works. 



Plate VII, Fig. 11. 



Toxocidaris erythrogrammus, the commonest rock urchin near 

 Sydney, sunk in self-dug pits in sandstone. On the right is a 

 vacant room. 



Plate VII, Fig. 12. 



A company of the Sydney Whelk, Pyrazus herculeus, Martyn, 

 crawling on the bare mud-flat. This place is situated in the 

 middle distance of Plate II, fig. 3. 



