. ALCYONOID POLYPS. 67 



In the Corallidae, the axis is wholly calcareous, and firm and 

 solid throughout, with usually a red colour, varying from crim.- 

 son to rose-red. Here belongs the Corallium riibrum, or pre- 

 cious coral. The polyp-crust or cortex, which covers the red 

 axis or coral, is thin, and contains comparatively few calca- 

 reous spicules, and consequently it readily disappears when the 

 dried specimens are handled. In an uninjured state, the polyp 

 centres may be distinguished over it by a faint six-rayed star, 

 A branch from a specimen obtained by the author at Naples, 

 is represented, of natural size, in the cut on page 66. The 

 polyps, as the enlarged view, by Lacaze Duthiers, shows, are 

 similar to those of other Alcyonoids — the tentacles being eight 

 in number and fringed. The figure represents the extremity 

 of a branch, magnified about four times lineally, with one 

 polyp fully expanded, two partly, and the rest unexpanded. In 

 the living Corallium, they open out thickly over the branches, 

 and make it an exceedingly beautiful object. The coral grows 

 in branching forms, spreading its branches nearly in a plane ; 

 and sometimes the little shrub is over a foot in height. The 

 author just mentioned states that, among the polyps, those of 

 the same branch are often all of one sex alone, and that besides 

 males and females, there are a few that combine both sexes. 



The precious coral is gathered from the rocky bottom of 

 the borders "of the Mediterranean, or its islands, and niost 

 abundantly at depths of 25 to 50 feet, though occurring also 

 even down to 1,000 feet. There are important fisheries on 

 the coast of Southern Italy ; of the island of Ponza, off the 

 Gulf of Gaeta ; of Sicily, especially at Trapani, its western ex- 

 tremity ; of Corsica and Sardinia, in the Straits of Bonifacio ; 

 of Algeria, south of Sardinia, near Bona, Oran, and other 

 places, which in 1853 afforded 80,000 pounds of coral; and 

 on the coast of Marseilles. The rose-coloured is the most 

 highly valued, because the rarest. 



Another species of Corallium was obtained by the author at 

 the Sandwich Islands (Atlas of Zoophytes, plate 60) ; but, while 

 probably from the seas of that region, its precise locality is 

 not known. 



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