178 



PEDICELLAEI^;. 



they are found. The annexed drawing will give a 

 general idea of their appearance in the Egg Urchin. 

 They are of three kinds, differing from each other in 

 the form of the head. Below, a hard, calcareous 

 column, slightly knobbed at each end, enclosed by 

 the stalk which is 

 slender there; but, 

 where the column 

 ends, widens into 

 what is called the 

 neck. This part, com- 

 posed of a tough 

 skin, is quite trans- 

 parent, and very 

 flexible, and while 

 life continues, it 



FEDICEIXARIJS. 



bends about in all 



directions. At the summit of this neck is a convex 

 head, crowned with three hard, calcareous teeth, beau- 

 tifully sculptured, and of three principal shapes ; some 

 long and slender, others short and very obtuse. A 

 more full account of their history and structure will 

 be found in Forbes's " Star-fishes," pp. 155 159. 



The shell of the Egg Urchin is not at all less curious 

 than the organs with which it is clothed. The globose 

 box in which the softer parts of the animal are shut up, 

 is by no means the simple crustaceous body which, at 

 first sight, it may seem to be ; but is built up of several 

 hundreds of pieces, accurately fitted together, like the 

 fragments which compose a fine piece of mosaic work. 

 The lines which separate them are scarcely visible 



