84 ECHTNODERMS OF THE BRITISH ISLES 



plates carry a series of 6-7 (5-8) short, blunt furrow spines, and 

 outside these two fairly regular longitudinal series of 4-5 small, 

 more grain-like spines. Dorsal plates with fine, glassy warts 



inside the circle of grains (Fig. 47). 

 R = ca. 1-8 r. Grows to a considerable 

 size, 95 mm. R., 63 r. being the largest 

 specimen recorded. Colour in life 

 f . j6S: •.• • "SyrcO^ yellowish-red. 



Biology and development unknown. 

 It has been taken several times 

 C'Helga", "Michael Sars ", etc.) off 

 the west coast of Ireland, in depths of 

 ca. 600-1450 m., but only a few speci- 

 mens at a time. Further known from 

 P ^<Xj:Sy the Bay of Biscay, off the coasts of 



Fig. 47.— Dorsal plates of Spain and Morocco, as far south as the 

 Plinthaster Perrieri. x 9. Cape Verde Islands, and at the Azores, 

 p. Groove of pediceiiaria. Bathj^metrical distribution ca. 600- 



1800 m. 

 Some authors regard this species as identical with the West 

 Indian PI. dentatus (Perrier). The present author does not feel 

 convinced of their identity, and therefore thinks it safest, at 

 least for the present, to keep the name PI. Perrieri for the East 

 Atlantic form. 



3. Nymphaster Sladen. 



Body pentagonal, with long, slender rays. Dorsal marginal 

 plates join in the mid-line of the rays for nearly their whole length ; 

 the dorsal plates confined to the disk, polygonal. Both dorsal, 

 marginal, and oral interradial plates covered with grains. Small 

 pedicellariae may occur on dorsal, marginal, and oral interradial 

 plates. 



One siiecies known to occur in the British seas. 



1. Nymphaster arenatus (Perner) . (Fig. 48.) 



(Syn. Pentagonaster arenatus Perrier ; Dorigona arenata (Perrier) ; 

 D. Jacqueti Perrier ; D. prehensiUs Perrier ; Nymphaster 

 protentus Sladen. (?) Pentagonaster {Dorigona, Nymphaster) 

 suhspinosus Perrier.) 



Marginal, dorsal, and oral interradial plates covered by a 

 uniform granulation, the grains being not placed so close as to 

 touch one another, and therefore round, not angular. Adambu- 



