248 ECHINODERMS OF THE BRITISH ISLES 



Ophiopluteus ramosus Mrtsn. may belong to this species. Biology 

 unknown, but very probably as in Ophiura. 



In British seas this species has been found in the Faroe 

 Channel (" Porcupine "), also recorded from 77 miles W.S.W. 

 of Fast net, Cape Clear, 720 m. (" Research "). It is chiefly a 

 cold-water species, distributed from the Arctic seas to Skagerrak, 

 and from Greenland to Massachusetts. Bathymetrical distribu- 

 tion ca. 5-ca. 4500 m. 



The Mediterranean Ophiocten abyssicolum (Forbes) seems to 

 represent only a variety of 0. sericeum, distinguished by the 

 scales of the disk being slightly larger and less numerous, the 

 arm spines shorter, and the papillae on the dorsal plates less 

 developed or even wanting. To this variety the specimens 

 known from the British seas will probably belong. Likewise the 

 form from the Bay of Biscay described under the name of Ophiocten 

 le Danteci Koehler no doubt belongs here ; at least all the charac- 

 ters given as peculiar to the single specimen known, 5 mm. of disk, 

 are found equally developed in specimens of 0. sericeum of a 

 corresponding size. 



2. Ophiocten scutatum Koehler. (Fig. 135.) 



Disk with large primary plates surrounded by a regular 

 circle of small, angular scales.^ Radial shields smaller than the 

 primary plates. Papillae across the arm base apparently divided 

 in two parts, a median part consisting of small, slender papillae, 

 and two lateral parts consisting of longer, club-shaped papillae. 

 No papillae found along outer edge of the proximal dorsal plates 

 of arm. These latter are very broad, roof-shaped, keeled. 

 Ventral plates merely contiguous in proximal part of arms, 

 farther out widely separated ; they are small, with a convex 

 outer edge and a small angle within. A single, very large, 

 leaf-shaped tentacle scale, which covers the pore completely ; 

 on the proximal pairs there is also a narrow scale at the outer 

 edge. Mouth shield much longer than broad, reaching nearly 

 to the edge of disk ; 3-4 mouth papillae, the outer one very broad, 

 scale-like. Colour in life unknown. Largest specimen known 

 8 mm. diameter of disk ; arms ca. three times as long as dia- 

 meter of disk. 



Biology and development unknown. 



^ A quite similar arrangement of the disk scales being found also in 

 young O. sericeum, it is probable that larger specimens of the present species 

 may show a similar arrangement and chai^acter of the disk scales as is found 

 in larger specimens of 0. sericeum. 



