GT BARRIER REEF OYSTERS Coral Rock Trap-door Cockscomb Saddle Black-edged 1893'Chromo Plate XIV; Great Barrier Reef Oysters; Fig. 1 and 2. Coral Rock Oyster, Ostrea mordax (Fig. 2 represents var. cucullata ), p. 246 Lateral and horizontal views; natural size; Fig. 3 and 4. Trap door Oysters, Ostrea mordax, var. cornucopioeformis, p. 248. Fig. 3, Lateral view; Fig 4, Dorsal view, with opercular valve removed, showing elongated hinge scar; natural size; Fig. 5. Cockscomb oyster, Ostrea crista galli, p. 244. Lateral view of small