50 



C. HEDLEY. 



sometimes browse on the marine pastures of Botany Bay 

 and furnish a meal to the blacks. 1 Posidonia leaves are 

 sometimes rolled and felted together by the waves into 

 compact balls; their fibre has lately been utilised in the 

 manufacture of cloth. 2 



Characteristic of 

 the local zostereta 

 is the Sydney 

 Cockle, Area tra- 



^'•'^ ll,l lv''''''n , n" lil ' l ''' !r !!!l"'..'"'»'V''' ,1 '"/'"'" , '''''^ / ' TO ''*' //W//// 



\ : >:;^'^T'-'*'*v <>/ . S"' 



pezia, a massive 

 boat-shaped, rib- 

 bed,white shell(fig. 

 14). The animal, 

 which protrudes a 

 large foot with a 

 distinct sole but no 

 byssus, is orange- 

 red, it is sluggish in 

 its movements and 

 usually rests sunk 

 in the mud for 

 three-quarters of 

 its length, often 

 bearing a tuft of 

 weed to mask the projecting anterior end. The tips of the 

 branchiae protrude above as short slender wavering ten- 

 tacles. Influence of environment is shown by its features. 

 For the purpose of diving quickly into the sand the shell of 

 Donax is smooth and wedge-shaped. But Area, being con- 

 structed to float on the surface of the mud, is moulded 

 posteriorly with a swell like a buoy and girdled with nodul- 



Fig. 14. Mud cockle, Area trapezia, with foot 

 extended and branchial tips exserted. The 

 anterior end projects above the surface of the 

 mud flat, the rest is buried beneath. 



1 Etheridge, Rec. Austr. Mus., vi, 1905, p. 17. 



2 Lucas, Proc. Linn. Soc. N.S. Wales, xxxiv, 1909, p. 498; Baker, op. 



cit., xxxv, 1911, p. 804. 



