§27. APPEARANCE OF THE LIVING CORALS. 627 



large branching stems, and others again exhibiting an elegant assem- 

 blage of interlacing twigs, of the most delicate and exquisite work- 

 manship. Their colours were unrivalled : vivid greens, contrasting with 

 more sober browns and yellows, mixed with rich shades of purple. 

 from pale pink to deep blue. Bright red, yellow, and peach-coloured 

 millepores clothed those fleshy masses that were dead, mingled with 

 beautiful pearly flakes of escharse and reteporae; the latter looking 

 like lace-work in ivory. Amidst the branches of the corals, like 

 birds among trees, floated many beautiful fish, radiant with metallic 

 greens or crimsons, or fantastically banded with black and yellow 

 stripes. Patches of clear white sand were seen here and there on the 

 floor, with dark hollows and recesses, beneath overhanging masses and 

 ledges. All these, seen through the clear crystal water, the ripple of 

 which gave motion and quick play of light and shadow to the whole, 

 formed a scene of the rarest beauty, and left nothing to be desired by 

 the eye, either in elegance of form, or brilliancy and harmony of 

 colouring." 



27. Coral reefs. — The vast accumulations of calcareous 



rocks in tropical seas, resulting from the consolidation of 

 the disintegrated skeletons of polyparia. have already been 

 alluded to, but the physical changes that are produced by 

 such apparently inadequate means require further conside- 

 ration, since they illustrate the formation of the coralline 

 rocks of the secondary and palaeozoic epochs. 



Id the Flustra foliacea of our coast (ante, p. 60S ), deli- 

 cate and brittle though it be. Ave perceive the elements of 

 those important changes to which the large lamellar corals 

 of tropical seas are giving rise. In the specimen before 

 us. you may observe that the base of the mass of Flustra. 

 which is about six inches in diameter, is already consolidated 

 by an aggregation of sand, that has rilled up the interstices. 

 On the surface are numerous parasitical shells and corals. 

 and between the convolutions of its foliated expansions, 

 echini. Crustacea, and other animals, have taken shelter; 

 while sand and mud have invested every cranny of the 

 lower third of the specimen, and imbedded serpula?. sabellae, 

 and fragments of many species of shells. It is evident. 



VOL. II. T T 



