372 THE INHABITANTS OF THE SEA. 



shrubberies ; and frequently the gigantic tridacna, embedded in 

 their calcareous parterres, discloses, on opening her ponderous 

 valves, her violet mantle tinted with emerald-green. The en- 

 chanted naturalist lingers for hours over the magnificent spec- 

 tacle, and forgets the lapse of time, as wonders upon wonders 

 crowd on his enraptured gaze. 



Bat the tropical coral-gardens serve not only as a harbour of 

 refuge to the numberless creatures that frequent their laby- 

 rinthine recesses, for many annelides, crustaceans, asterias, and 

 even fishes, feed upon their animal flowrets. Among these, 

 the Scari are provided with a very remarkable dental apparatus 

 to protect their mandibles from injury while biting the cal- 

 careous corals. These fishes have their jaws, which resemble 

 the beak of a parrot (whence they receive their usual appellation 

 " parrot fishes "), covered externally with a kind of pavement of 

 teeth, answering the same purpose as the horny investment of 

 the mandibles of the bird. The teeth that form this pavement 

 are perpetually in progress of development towards the base of 

 the jaw, whence they advance forward, when completed, to 

 replace those which become worn away in front by the constant 

 attrition to which they are subjected. Thus armed, the Scari 

 browse without difficulty on the newest layers of the stony 

 corals, digesting the animal matter therein contained, and 

 setting free the carbonate of lime in a chalky state. Many of 

 the Diodons, Chastodons, and Balistse or file-fishes, of which 

 Kittlitz saw some new species, one still more splendid than the 

 other, in every lagoon-island he visited in the long range of 

 the Carolines, likewise feed upon corals, and possess a dental 

 apparatus fit for masticating their refractory aliment. The 

 Diodons have grooved teeth, excellently adapted to crush and 

 bruise, and the Balistse have eight strong conical teeth in every 

 jaw, with which they easily nip off the shoots of the coral bushes. 



Of the reef-building corals it may well be said that* they 

 build for eternity. The bones of the higher animals vanish 

 after a few years, but the stony skeleton of the -polyp 

 remains attached to the spot of its formation, and" serves 

 as a basement or stage for new generations to build upon. 

 Life and death are here in concurrent or parallel progress ; 

 generally the whole interior of a corallum is dead. The 

 large domes of the astrceas are in most species covered 



