ACTINOIDA. 687 



STTB.ORDER ALCYONARIA. 



Family Pennatulida. SEA-PENS. This interesting family of 

 Corals is represented on the Chart by Pennatula phosphorea? 

 which has a stony axis and is free or has the base sunk in the 

 mud. From the axis a series of lateral branches passes off on 

 each side, resembling the barbs of a feather, whence the generic 

 name. On these branches the polyps are situated. This spe- 

 cies, when disturbed, emits a phosphorescent light. By the 

 movement of the eight tentacles, the animal seems to have power 

 to direct its course. 



Family Gorgonida. SEA-FANS. These have the polyp mass 

 rooted and tree-like, consisting of a central axis backed with a 

 polypiferous crust. The axis is horny or fasciculate, but not cal- 

 careous. These include many beautiful fixed corals. Some Gorgo- 

 nias found on the Atlantic coast, when stripped, have the appearance 

 of Whale-bone. The WARTY SEA-FAN, G. verrucosa, is somewhat 

 fan-shaped, and when dry, backed with a white warted crust. 

 The species G. flabellum, (Lat. a small fan,) is reticulated with 

 the branches inwardly compressed. It is found in the warm seas 

 of India and America, and three feet in length. 



The RED CORAL, Coralium rubrum, (see Chart,) has the entire 

 stem converted into a stony axis ; the flesh is external, and in 

 this alone are the polyp cells. This species is branched, one 

 foot high, varying from a deep red to a beautiful rose color. It 

 takes a high polish, and is employed for purposes of ornament. 



Our limits render it necessary to omit details of other families 

 of Corals, some of which are found in American seas ; also many 

 particulars respecting the wonders wrought by the Coral-insects. 

 The statements of Prof. Dana contained in our general remarks, 

 preclude the idea that the coral islands, of which so much has 

 been said, are exclusively the work of these insects. In many 

 instances the coral extends to a much greater depth than these 

 animals are known to live ; in other instances it presents a sur- 

 face considerably elevated ; but corals " cannot grow above the 

 surface." Com. Wilkes, (of U. S. Exploring Expedition,) and 

 others, regard them as in part at least, of volcanic origin. Some 

 subterranean movement must have lifted these islands from the 

 bed of the ocean ; the coral being in some instances not less than 

 eight or nine thousand feet high. Agassiz, it is said, has for the 

 first time succeeded in preserving alive in this country, some co- 

 ral insects. They were kept in water, carefully and frequently 

 changed. Lady Wortley, (see her " Travels in the United States," 



