124 CORALS AND CORAL ISLANDS. 



Gulf a ship had her copper bottom encrusted in the course of 

 twenty months, with a layer of coral two feet thick, — evi- 

 dently to be accepted hesitatingly. He also speaks of a chan- 

 nel in the lagoon of Keeling atoll having been stopped up in 

 less than ten years ; and of the natives of the Maldives find- 

 ing it necessary occasionally to root out, as they express it, 

 coral knolls from their harbors. 



Mr. Stutchbury describes a specimen consisting of a spe- 

 cies of oyster whose age could not be over two years, encrust- 

 ed by an Agaricia weighing two pounds nine ounces ; but he 

 does not state whether the shell was that of a living oyster 

 or not. 



Dr. D. F. Weinland states that on Hayti, in a small coral 

 basin between the town of Corail and the island Caymites, 

 never disturbed by vessels on account of the small depth of 

 water, he observed several branches of the Madrepora cervi- 

 cornis projecting above the surface of the water from three to 

 five inches, all of which, down to the water level, were dead, 

 as a result evidently of exposure to the air. This was in the 

 month of June. He adds that all along the north shore of 

 Hayti, the water level is from four to six feet higher in the 

 winter season than during summer ; and suggests that the 

 growth of three to five inches, above referred to, might have 

 been made during the three winter months. 



Duchassaing (in L'Institut, 1846, p. 117) observes that in 

 two months some large individuals of Madrepora prolifera 

 which he broke away, were restored to their original size. 

 More definite and valuable is the observation of Mr. L. F. de 

 Pourtales, that a specimen of Mceandrina lahyrinthica, meas- 

 uring a foot in diameter, and four inches thick in the most 

 convex part, was taken from a block of concrete at Fort Jef- 

 ferson, Tortugas, which had been in the water only twenty 



