no 



ECHINODERMS OF THE BRITISH ISLES 



Only one species known with certainty from the British seas, 

 but another species, Korethr. setosus Perrier, is very likely 

 to occur there also. In fact it is probable that some young 

 specimens taken by the " Helga " at 54° 17' N., 11° 33' W. 

 (388 fms.), and 5r^20' N., 11° 41' W. (468-560 fms.), should be 

 referred to this species.^ The main characters distinguishing this 

 species from K. hispidus are given in the key. 



Key to the species of Korethraster known from or likely to occur 

 in the British seas. 



4 spines to each side of jaws. No circle of larger plates in centre 

 of disk \. K. hispidus W. Th. 



3 spines to each side of jaws. A circle of 5 larger plates in centre 

 of disk ...... K. setosus Perrier 



1. Korethraster hispidus Wyv. Thomson. (Fig. 65.) 



Paxillse consisting of 6-10 long, very slender spines, with an 

 oval thickening at the base. The plates nearest the centre of the 

 disk not larger than the other dorsal plates. A rather deep 

 furrow in the interradial mid-line without the usual polygonal 











Fig. 65. — Korethraster hispidus. Slightly enlarged. 

 (After Sladen, " Challenger " Ast.) 



plates ; these furrows (which are concealed by the paxillse) unite 

 in the centre of the disk and thus divide the dorsal side into five 

 segments. Jaws with four spines on each side, the spines on the 

 outer surface strong, with the outer part hyaUne. R = ca. 1-6- 



1 Cf. Farran, " The Deep-water Asteroidea, Ophiuroidea, and Echinoidea 

 of the West Coast of Ireland " {Fisheries, Ireland, Sci. Invest., 1912, 

 vi. (1913), p. 23). 



