214 



ECHINODERMS OF THE BRITISH ISLES 



3. Amphiura denticulata Koehler. (Fig. 121.) 



Disk covered with scales only on the dorsal side, the ventral 

 side completely naked ; primary plates not distinguishable. 

 Radial shields separated by a wedge of scales, sometimes contiguous 

 at the distal end. Dorsal plates of arms rounded. Ventral plates 

 pentagonal, with slightly concave outer edge. Five to seven arm 

 spines ; the lowermost and uppermost smooth, conical, the others 

 slightly flattened, with distal edge serrate, proximal edge smooth ; 

 often there is a small terminal hook. No tentacle scale. Mouth 

 shields with a small, rounded outer lobe ; outer mouth papilla 

 small, conical. Colour in life unknown. Diameter of disk up to 

 5 m.; length of arms ca. 10 times the diameter of disk. 



Fig. 12] 



-Amphiura denticulata ; part of oral (1) and dorsal side (2) ; 

 arm spine (3). x 15. 



In British seas this species has been found in the Faroe 

 Channel (61° 07' N., 9° 33' W., 750 m., " Michael Sars "). Else- 

 where known only from Greenland to Newfoundland. Bathy- 

 metrical distribution 155-1100 m. 



4. Amphiura filiformis (0. F. Miiller). (Fig. 120, 3-5.) 



Disk covered with scales on dorsal side onl}^, ventral side 

 naked ; scales rather coarse, primary plates not distinguishable. 

 Radial shields separate. Dorsal arm plates transverse oval ; 

 ventral plates with concave outer edge and somewhat produced 

 outer corners ; the proximal ventral plates may have a more 

 or less distinct median keel. Five to seven arm sjoines, the second 

 from below with the point axe-shaped widened (Fig. 120, 5). No 



