PRESIDENTIAL ADDRESS. 53 



The eyes are mounted half way on stalks which finish as 

 slender lashes waved incessantly hither and thither. On 

 the tail are planted two waving filaments, while the front 

 margin of the foot is also provided with a pair of processes. 

 A triangular shell about eight inches long, related to the 

 mussels is Pinna menkei. Its habit is to sink upright in 

 the mud, and to present to a bare footed visitor a thin 

 concave blade capable of inflicting a severe wound. Among 

 the narrow zostera leaves lies commonly hid the slender 

 zostera Pipe-fish Stigmatophora argus (fig. 17). So like is 



Fig. 17. The Pipe-fish of the zosteretum, Stigmatophora argus. 



this to its natural surroundings that, whether straight or 

 curled, the eye can scarcely detect it even in full view. 

 And if detected and pursued the Pipe-fish escapes from 

 every enemy by diving into the dense weed. The males 

 carry the incubating eggs in a pouch on the tail. 



Occasionally the zosteretum is invaded by the Bubble- 

 weed, Colpomenia sinuosa. 1 This pest spreads over the 

 flat, smothering other vegetation and attaching itself to 

 the oysters, whelks or cockles. When the gas forms in the 

 expanding balloon it lifts the shell and floats it away, so that 

 oyster plantations are sometimes seriously denuded by its 

 agency. 



A peculiar development of the zosteretum formation is 

 the ruppia-lagoon, of which Deewhy Lagoon (Plate VI) a 

 few miles north of Sydney may be selected as a typical 

 example. Here a sand -bank thrown up by the surf has 

 dammed the mouth of a small stream. Behind this barrier 

 the water accumulates in a shallow brackish lake, several 



1 Stead, Proc. Linn. Soc. N.S. Wales, xxxvi, 1912, p. 632. 



