296 



COM PA RA T[ VE ANA TOM Y 



CHAT. 



SUB-CLASS 2. Euasteroidea. 

 Asteroidea with paired, i.e. opposite ambulacral plates or "vertebra?." 



Order 1. Phanerozonia. 



Asteroidea with large, strongly developed, marginal plates. The inframarginal 

 and supramarginal plates are closely fitted together. Papulae (branchial vesicles) 

 only occur on that surface of the body which is surrounded by the supramarginal 





FIG. 239. Ctenodiscus procurator (after Sladen), from the oral side, 

 stomach is visible through the mouth. 



A Gastropod in the 



plates, i.e. on the apical or upper side. Ambulacral plates broad. In each ambu- 

 lacral furrow there are two longitudinal rows of tube-feet. The adambulacral plates 

 are prominent in the oral skeleton. Where pedicellarise occur they are sessile. 



Fam. 1. Archasteridae : Parar chaster, Dy taster, PI ut< master, Pseudarchaxt* ,\ 

 Archaster, etc. Fam. 2. Porcellanasteridse, the centre of the apical system pro- 

 duced into a more or less long outgrowth : Porccllanastcr, Hyplinl aster, CtenotHwn* 

 (Fig. 239), etc. Fam. 3. Astropectinidae, without anus and usually without pedicel- 

 larite : Astropecteu, Bathybiastcr, llyastcr, Luidia, etc. Fam. 4. Pentagonasteridae : 

 Pentagotutster, Astrogonium, Ncctria, Calliaster, Stellastcr, Goniodiscus, Mimaster, etc. 

 Fam. 5. Antheneidse : Anthcnea (Fig. 240), Goniastcr, etc. Fam. 6. Pentacerotidse : 



