ASTEROIDEA 109 



disappear in the delicate meshwork of the basal part (Fig. 64). 

 Supra-dorsal and actino-lateral membrane thick and fleshy, not 



Fig. 64. — Spine of segmental aperture of Hymenaster giganteus. x 13. 



pellucid. R. = ca. 1-6 r. Reaches a very considerable size, ca. 

 26 cm. diameter. Colour in life deep blood-red. 



Known only from off S.W. Ireland, 527-1350 m. (" Flying 

 Falcon ", " Helga "). 



IV. Family Korethrasterid.e 



Dorsal side with paxillae, formed by very long, fine spines, 

 not covered by a supra-dorsal membrane. No fin-like (actino- 

 lateral) membrane. No larger marginal paxillse. No oral inter- 

 radial plates. Spines of adambulacral plates forming together 

 with those of lower marginals a single transverse series, not 

 webbed. Rays mostly five. 



This family forms a transition between the Pterasteridae and 

 Solasteridae, having characters in common with both. 



Onl}^ one genus represented in British and European seas. 



1. Korethraster Wj^v. Thomson. 



Rays short. Plates of the dorsal side, carrying the paxillae, 

 polygonal or rounded, imbricating upwards. No papulae between 

 the dorsal plates. Spines of the paxillae enclosed by a common 

 skin-sheath, leaving the outer part free. Jaws Avith a strong 

 spine on outer surface on each side of mid-line. One furrow 

 spine. Adambulacral and marginal spines flattened, somewhat 

 fan-shaped, made up of coalesced fine spines. 



