324 THE ZOOLOGIST, 



their respective theories of origin of coral reefs. The remarks on 

 the evidence which exists of a former connection between New 

 Guinea and North Queensland (pp. 132, 133) are particularly 

 instructive. 



In Chapter V. (pp. 139 — 203) we have a detailed and beauti- 

 fully illustrated account of corals and coral animals, succeeded 

 by another on pearl and pearl-shell fisheries, the annual value of 

 which is estimated at ^670,000. This industry is confined to the 

 tropical area of the Queensland coast-line, or, in other words, is 

 essentially associated with the Great Barrier district. Its head- 

 quarters are at Thursday Island, Torres Strait, the northernmost 

 point of the Australian continent. All the licenses for vessels, 

 boats, and men employed in this fishery are taken out at 

 Port Kennedy, Thursday Island ; and from this centre shelling 

 expeditions are made along the mainland coast line to the 

 northern limits of the Great Barrier Coral Eeef, and throughout 

 Torres Strait northwards to the vicinity of New Guinea. Of late 

 years pearl-shell has been also obtained in some quantity on the 

 east shore of Cape York peninsula in the Gulf of Carpentaria. 

 The average depth of water from which the greater quantity of 

 mother-of-pearl shell is at present collected is seven or eight 

 fathoms. Twenty fathoms represent about the greatest depth 

 from which the shell is profitably fished, although few divers can 

 stand the strain of prolonged work under that pressure. In 

 former years it was abundant, and even now is occasionally 

 obtained, in such shallow water as to be gathered by the hand 

 at low spring tides. 



The very best shell fetches from £8 to £9, and the worst 

 about £3 per cwt. The species which bears this commercial 

 value is Meleagrina margaritifera, the typical mother-of-pearl 

 and pearl-producing shell of the Indian and Pacific Oceans. Two 

 varieties, the one with a golden edge, the other having a silvery 

 or nacreous consistency throughout, are pretty evenly inter- 

 mingled, and do not, so far as the author's investigations have 

 extended, present any marked distinction in the aspect or 

 structure of the contained animal. The last-named variety 

 having the nacreous lining, or true mother-of-pearl, pure and 

 uniform throughout, is the more valuable, as it cuts up to 

 greater advantage, and for commercial purposes the purest white 

 blull invariably commands the highest price. 



