ECUINODERMATA. Q47 
Fahr., nor at greater depth than twenty fathoms. The 
most luxuriant reefs are in the Central and Western 
Pacific and around the West Indies. 
(2) Sclerobasic Corals—Corallium rubrum, the precious 
coral of commerce, is shrub-like, about a foot high, solid 
throughout, taking a high polish, finely grooved on the 
Fie. 204.—Sea-fan (Gorgonia) and Sea-pen (Pennatula). 
surface, and of a crimson or rose-red color. In the living 
state the branches are covered with a red ccenosare stud- 
ded with Polyps. Gorgonia, or “Sea-fan,” differs from 
all the other representative forms in having a horny axis 
covered with calcareous spicules. The branches arise in 
the same vertical plane, and unite into a beautiful net- 
work. 
Subkingdom EcurnoprerMarTa. 
The Echinoderms, as Star-fishes and Sea-urchins, are dis- 
tinguished by the possession of a distinct nervous system 
(a ring around the mouth); an alimentary canal, complete- 
ly shut off from the body-cavity, and having both oral and 
anal apertures; a peculiar system of circular and radiat- 
