298 COMPARATIVE ANATOMY chap. 



Fam. 1. Linckiidse : Chaetaster, Ophidiasler, Linckia, Metrodira, etc. Fam. 2. 



^ffim 



Fic. 242. — Hymenaster cselatus (after Sladen), with arms bent back. 



Zoroasteridse : Zoroaster, Cnemidastcr (Fig. 241). Fam. 3. Stiohasteridae : Sti- 

 ehastcr, etc. Fam. 4. Solasteridse : Solastei; Crossnstcr, Oorethraster, etc. Fam. 5. 



Fnj. 248.— Hymenaster nobilis (alter Sladen), from the oral side, | natural size. 



PterasteridsB, with brood cavity on the apical side of the disc : Pteraster, Retastcr, 

 Hymenaster (Figs. 242 and 243), Myxastcr, Bcntkastcr, Pythonaster, etc. Fam. 6. 



