88 ECHIN0DERM8 OF THE BRITISH ISLES 



numbers ; also recorded from the Rockall Bank. It is not known 

 to the south of the British area ; to the north it is distributed 

 along the Scandinavian coasts as far north as the Murman coast ; 

 also known from S. Greenland to ca. 38° N. along the American 

 coast. Further, it occurs in the Northern Pacific. Bathy- 

 metrical distribution, 15-ca. 2500 m. 



The variety is known hitherto only from the Scandinavian 

 seas and from west Greenland. 



Subfamily Hippasteriin^ 

 5. Hippasteria Gray. 

 (Syn. Hippasterias.) 



Disk large, arms short. Dorsal side with thick spines, sur- 

 rounded by a circle of smaller grains. Marginal plates with a 

 thick, prominent spine. Numerous large bivalve pedicellariae. 



Only one species in British (and European) seas. (Several 

 other species in the North Pacific.) 



1. Hippasteria 2^hrygiana {Farelms) . (Fig. 50.) 



(Syn. Goniaster, Aslrogonium p/ir?/r//a7iwm ; Goniaster equestris 

 (Forbes) ; Hippasteria plana (Linck) ; Hippasteria europcea 

 Gray ; H. Johnstoni Gra}-.) 



Plates of dorsal side of various sizes ; larger ones wdth a thick 

 spine or a pedicellaria in the middle and a series of grains around 

 the edge, and smaller ones irregularly disposed among the former, 

 carrying grains or pedicellariae. Marginal plates each with 1-3 

 thick spines in the middle and a series of grains along the edges. 

 Oral interradial area very large, with numerous large pedicellariae, 

 each surrounded by a circle of grains (Fig. 26, 4). Along the 

 ambulacral furrow the pedicellariae are arranged in a fairly 

 regular longitudinal series, each pedicellaria standing obliquely 

 to the furrow. 2-3 robust furrow spines ; on the outer surface 

 of adambulacrals generally only one large spine. R = ca. 2 r. 

 Colour in life beautifully red. Grows to a very considerable size, 

 ca. 200 mm. R. 



It feeds on echinoderms, mussels, worms ; apparently also 

 on detritus. Development unknown, but its large, yolky eggs 

 indicate that it has probably direct development, without a 

 pelagic larval stage. 



In British seas it has been recorded from Plvmouth Sound, 



