298 COMPARATIVE ANATOMY CHAP. 



Fam. 1. Linckiidse : Chaetaster, OpMdiaster, Linekia, Metrodira, etc. Fam. 2. 



FIG. 242. Hymenaster caelatus (after Sladen), with arms bent back. 



Zoroasteridse : Zoroaster, Cnemidaster (Fig. 241). Fara. 3. Stichasteridse : Sti- 

 chastcr, etc. Fam. 4. Solasteridse : Sol-aster, Crossastcr, Corethraster, etc. Fam. 5. 



FIG. <243.- -Hymenaster nobilis (after Sladen), from the oral side, f natural size. 



Pterasteridse, with brood cavity on the apical side of the disc : Pteraster, Retaster, 

 Hymenaster (Figs. 242 and 243), Myxaster, Benthaster, Pythonaster, etc. Fam. 6. 



