528 DESCRIPTION OF THE MUSEUM. 



the ananchites striata, which is found in a fossil 

 state in the chalk at Meudon, near Paris; the 

 echinus melo, which is sometimes more than 

 8 inches in diameter ; the echinus esculentus and 

 the lividus, which are eaten by the inhabitants of 

 Mediterranean coasts; the ech. variegatus, ra- 

 diatus and atrctius, which have variegated colours, 

 and the ech. tuberculatus,* whose spines are im- 

 planted on large round tubercles; the cidarites 

 imperialis, verticillaris , calamarius, baculosus, 

 whose spines are very remarkable ; and the cid. tri- 

 buloides, which has close to its mouth a short 

 spine in the form of a club : this remark acquires 

 a degree of interest from the great number of 

 ^ similar bodies which are found in a fossil state. 



The Jistulides, which compose the third sec- 

 tion, have a tough fleshy skin: they have been 

 divided into five genera ; twenty species of them 

 are placed next to the radiaria and to the mol- 

 lusca preserved in spirits. \Ve shall only notice 

 the sipunculus edulis, which lives buried under 

 the sand in the Indian seas. 



The class we have ^et to examine is that of 

 the polypi, the last in the animal kingdom ; they 

 are complex animals, some of them naked, others 

 protected by an envelope which they construct 

 and inhabit in common, and which is extremely 

 remarkable, 



