Till 



EOHINODERMA TA—t< YSTEMA TIC RE VIE IV 



301 



Order 2. Euryalse. 



Arms simple or branched, can be rolled up vertically towards the nioutli. Only 

 rudimentary shields are found below the soft but thick outer integument. Without 

 spines. In forms with unbranched arms there are usually 5 buccal shields, one of 

 which is the madreporitic plate. Most of the forms with branched arms liave no 



Fig. 246. — Astropliyton Lincki (Miillor and Troscliel), from the oral side (original). 



distinct buccal plates. There is then either a single raadreporite in an oral inter- 

 brachial area or else there are 5 interbrachial madreporites. 



Single Fam. Astrophjrtidae : Astrophyton (Fig. 246), Gorgonoceplmlus, EuryaU, 

 Trichaster (arms slightly and only at their tips, dichotomously branched), Astroclon 

 (the same), Astrocnida (the same), Astroporpa (arms undivided), Astrogmn^jlius (the 

 same), Astrochele (the same), Astrotoma (the same), Astroschema (the same), Opliio- 

 creas (the same), etc.^ 



' For a more recent classification of Opliiuroidea, see F. J. Bell, Proc Zool. Soc. 

 London, 1892, pp. 175-183. 



