ECHINODERMATA : CRINOIDEA. 



207 



the base, first dichotomously, and then into many branches. 

 In Ophiura, the Sand-star, the arms serve for reptation (creep- 



Fig, loo. Ophiuroidea. a Opkiura texturata, the common Sand-star; 

 b Ophiocoma neglecta, the grey Brittle-star. (After Forbes. ) 



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

 disc many times in length. 



The order Ophiuroidea may be divided into two families, as 

 follows : 



Family I. Euryalidce. 



Arms branched ; genital fissures ten in number. 

 Fam. 2. Ophiurida. 

 Arms simple ; genital fissures, mostly five in number. 



CHAPTER XX. 

 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 



