452 



EADIATA: ECHINODERMATA. 



The Ophiurans have no teeth, but in place of teeth 

 hard ridges. They have no interambulacral spaces or 

 plates; but a single series of large plates envelop the 



FIG. 683. 



"Basket-fish," Astrophyton Agassizii, Stimpson. 



whole of each arm, meeting in a ridge along the middle 

 of its under surface. They have no true suckers like those 

 of Star-fishes, etc. ; but in place of these they have rough 

 or tuberculated organs, which pass out through the numer- 

 ous holes in the sides of the arms. Their madreporic body 

 is one of the circular plates on the under side of the disk ; 

 and the ovarian openings are in each side of the arms, at 

 the base. 



Most of the Ophiurans have the arms simple ; but one 

 kind the Astrophyton which attains a diameter of ten 

 or twelve inches, has the arms extensively branched, the 



