OPHIUROIDEA 169 



spines. The upper one is, as a rule, somewhat coarser and longer 

 than the others. Diameter of disk up to ca. 20 mm. ; arms ca. 

 four times the diameter of the disk. Colour in life unknown. 



In British seas this species has been found in the Faroe 

 Channel, 59° 56' N., 6° 27' W., 653 m. (" Porcupine "), and off 

 S.W. Ireland, in 687-1224 m. (" Helga "). It has elsewhere been 

 recorded from off the Azores and from Denmark Strait, and is 

 thus evidently distributed over the whole of the N.E. Atlantic. 

 Bathymetrical distribution ca. 600-1200 m. 



2. Ophioscolex Miiller and Troschel. 



Disk naked or with scattered small spines ; the skin contains 

 numerous fine, glassy scales. No larger marginal scales. Radial 

 shields indistinct or in the form of more or less distinct ridges. 

 Mouth papillae spine-like, as are also the teeth, which are arranged 

 in a single series, only exceptionally, in large specimens, in a small 

 cluster on apex of jaw. 



Two species known from the British (and European) seas.^ 



Key to the species of Ophioscolex known from the British 

 (and European) seas. 



Disk entirely naked ; no tentacle scales 



1. O. glacialis Miill. and Troschel 

 Disk with small spines ; one slender tentacle scale 



2. O. purpureus Diib. and Kor. 



1. Ophioscolex glacialis Miiller and Troschel. (Fig. 95, b, e.) 



Skin of disk quite naked. Dorsal plates of arms rudimentary, 

 scarcely observable without a special microscopical examination ; 

 what is seen along the dorsal side of the arms in dried specimens is 

 the dorsal side of the vertebrae. Ventral plates well developed, 

 contiguous, with slightly convex distal edge. 3, exceptionally 4, 

 slender arm spines, which are not transformed into hooks in 

 distal part of arms. No tentacle scales. 3-6 slender mouth 

 papillae on each side, chiefly on inner part of jaw ; in large 

 specimens there may be a group of papillae on apex of jaw. 

 Mouth shield small, triangular ; adoral shields each with a spine. 

 Diameter of disk up to ca. 25 mm. ; length of arms ca. five times 

 the diameter of disk. Colour in life yellow, reddish or violet. 



It is strongly phosphorescent on the arms. Lives on muddy 



bottom. 



^ The "Ophioscolex retectus"' Koehler from the Bay of Biscay 

 ("Caudan") is no Ophioscolex but an Ophiolebes (of the Ophiacanthidae). 



