Boone, Mollusca, Cruises of "Ara" and "Alva" 325 



References : Ostrea cucullata Born, Test. Mus. Caes. Vindobon, 

 1780, p. 122. 



Ostrea mordax variety co^mucopiaeformis, Saville Kent, The 

 Great Barrier Reef of Australia, 1893, London, p. 249, chrome 

 plate 14, figs. 1, 2, 3, 4. 



Ostrea cucullata, Hedley, Charles, in Marine Mollusca of 

 Queensland, published as appendix, in Rept. Austral. Assoc. Adv. 

 Sci., Brisbane, Queensland, vol. XII, p. 365. 



Family: TRIDACNIDAE 



Genus: TRIDACNA Lamarck 

 Tridacna crocea Lamarck 



Plates 138 and 139 



Type : Lamarck*s type came from the Indian Ocean and was 

 first deposited in his cabinet, now in the Paris Museum. 



Distribution: This species is widely distributed in the lit- 

 toral zone, usually in coral reefs, where it burrows in dead coral, 

 from Aden and the Persian Gulf eastward through the Indo-Pa- 

 cific in the Mergui Archipelago, Andaman Islands, Nicobar Is- 

 lands, the Dutch East Indies, Singapore, the Gulf of Siam, the 

 Philippines, Loo Choo Islands, Moluccas, Australia: Cape York, 

 8 fms. (E. A. Smith) ; Hope Islands (Hedley) ; Dunk Island, 

 Queensland (Eanfield) ; Low Islands, Queensland (Whiteley and 

 Boardman) ; Lifu, New Ireland, Rarotonga and Society Islands. 



Material examined: Two specimens from Teviatoa Reef, 

 Raiatea Island, Society Islands, August 21, 1931 ; two specimens 

 from Venus Point Reef, Tahiti, Society Islands, August 15, 1931. 



Discussion: This species is one of the three smaller Aus- 

 tralian members of the Tridacnidae that burrow in dead coral. 

 The shell possesses the very large pedal aperture, which distin- 

 guishes the boring from the perching species. The large, mush- 

 room-shape foot protrudes through this aperture and excavates 

 the cell in the coral, which is smooth inside and occupies consider- 

 able space within the rock to permit free movement of the mol- 

 lusk and the opening and shutting of its valves. The entrance to 



