148 



MANUAL OF ZOOLOGY. 



ing), and are undivided, often exceeding the diameter of the 

 disc many times in length. 



Fig. 41. Ophiuroidea. a Ophiura texturata, the common Sand-star; b Ophiocoma 

 neglecta, the grey Brittle-star (after Forbes). 



The order Ophiuroidea may be divided into two families, as 

 follows : 



Family I. Ophiuridea. 



Genital fissures two or four in number. Arms five, always simple. 

 Family 2. Asterophydice. 



Genital fissures ten in number. Arms five, simple or branched. 



CHAPTER XXI. 

 CRINOIDEA, CYSTOIDEA, AND BLASTOIDEA. 



ORDER CRINOIDEA. The members of this order are Echino- 

 dermata, in which the body is fixed, during the whole or a portion 

 of the existence of the animal, to the sea-bottom by means of a 



