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CLASS X. ECHINODERMA. 



Remarks. The organic structure of the ani- 

 mals of this class is more complicated than that of 

 any other class of this division. They have an 

 organized covering, often sustained upon some- 

 thing resembling a skeleton, which supports sharp 

 processes or spines sometimes moveable. They 

 have an imperfect vascular system, and their res- 

 piratory organs are often very distinct. Some 

 species have fibres, which seem to supply the of- 

 fice of nerves. 



ORDER 1. PEDICELLATA. 



Having stem-like moveable processes which per* 

 /orm the office of feet. 



ASTERIAS, (sea-star,) body depressed, covered 

 with a coriaceous crust, muricate with tentacula^. 

 and grooved beneath ; mouth central, five-rayed* 

 In sea. 



E^CRINUS, (stone-lily.) a stein divided into nu- 

 merous articulations ; its branches are like the 

 stem, and subdivided dichetomously. Its fossil 

 remains have been called entrochites, which are 

 pieces of the stems and branches of this genus. 



ECHINUS, (sea-urchin, sea-hedghog,) body 

 roundish, covered wdth a bony sutured crust, and 

 generally furnished with moveable spines ; mouth 

 placed beneath, and mostly five-valved. In sea. 



HOLOTHURIA, body detached, cyliridric, thick^ 

 naked, and open at the extremity ; mouth sur- 

 rounded by fleshy branches, tentacula or feelers. 

 In sea. 



