Sub-kingdom CENTRONI^E, fPallas.) 



Section Echinodermata. 



Body more or less protected by a shelly covering, composed of variously shaped 

 calcareous plates imbedded in the substance, attached to the sm-face of the skin, or 

 forming the indurated frame work of the animal. These pieces are formed by the 

 deposition of earthy particles round certain central points, so that when fully developed, 

 they observe a weU-defuied arrangement, which is easily traceable into certain distinct 

 forms, each pecidiar to its kind. This calcareous skeleton, thoiigh formed of numerous 

 pieces, contmues fii-mly luiited during the animal's life ; but after death, in consequence 

 of the habUity of the investing membrane and connecting fibres to destruction, the 

 bone-hke plates and joints become incoherent. By the mode of structure pointed out, 

 the increase of the animal, as regards the size and nimiber of the plates, is duly provided 

 for; and injuries of the plated envelope, from external violence, are readily repaii'ed by 

 the renewed deposition of calcareous matter. 



AU the known Echinodermes are marine, and are sustamed by animal food. 



Class 1. PiNNASTELLA, OR Crinoidea. Piiuii<jrada, (Forbes.) 



Character of the class. — Viscera protected by an indui'ated skeleton formed of cal- 

 cai'eous plates ; mouth surrovuided by pinnated rays composed of calcareous joints. 

 Sometimes fi-ee, but more fi-equently permanently attached (dorsally) to other bodies by 

 a jointed flexible column. 



Order 1. Cionacineti. 

 Elym. KliiN (cion) a column, and AKINHTOS (acinetos) fixed. 

 Fixed to extraneous objects by a jomtcd flexible column. 



