TYPE EOHINODEBMA. 



675 



cate canals. These organs, which, are usually quite small, 

 are situated in the yicinity of the ambulacral pores or near 

 the mouth, and are supposed to haye a sensory, perhaps 

 olfactory, function. 



Owing to the presence of the firm test the muscular system 



pp an tt 



is but feebly developed, being represented by the muscles 

 attached to the spines, pedicellarise, etc., and by those which 

 move the parts of the masticatory apparatus when it is 

 present. 



The coelom (Fig. 265, Co) is comparatively spacious, though 



