18 



ECHINODERMS OF THE BRITISH ISLES 



Distal edges of arm-joints produced, overlapping the bases of 

 the succeeding joints, the dorsal profile of the arm thus being 

 serrate. Axillary markedly broader than long, distinctly 

 shorter than the preceding joint . Bathycrinus Wyv. Th. 



Distal edges of arm -joints not produced, dorsal profile of arm 

 smooth ; axillary scarcely broader than long, about as long as 

 the preceding joint . . . Ilycrinus Dan. and Kor. 



Fig. 6. — Calyx, basal part of arms and upper end of stalk of Rhizocrinus 

 lofotensis (1) and Ilycrinus Carpenteri (2). x 9. 



1. Rhizocrinus M. Sars. 



Basals distinctly higher than the radials, completely fused 

 into a solid conical, cup-shaped ossicle, without sutures (Fig. 6, 1); 

 also the radials partly coalesced with the basal cup. Muscular 

 and non-muscular (ligamentous) articulations alternating regu- 

 larly throughout the arm. 4-7 arms. 



Only one species in British (and European) seas. 



