200 



ECHINODERMS OF THE BRITISH ISLES 



4. Dorsal plates of arms fan-shaped, with convex outer edge ; spines 



on dorsal side of disk ; radial shields not very broad (Fig. 114) 



2. O. abyssicola M. Sars 



Dorsal plates rhombic, outer edge with a rounded peak ; no spines 



on dorsal side ; radial shields very broad. (" Challenger'' Oph. 



PI. XIX. 16-18) ..... O. canotia Lyman 



5. Radial shields contiguous in distal half . O. Lymani Ljungm. 

 Radial shields separate ....... G 



6. Two mouth papillae on each side of jaw. Four arm spines . 7 

 One mouth papilla on each side of jaw. Three arm spines^ 



O. profundi Ltk. and Mrtsn. 



7. Dorsal plates of arms elongate -oval. Large genital slits (Fig. Ill) 



O. nidarosiensis Mrtsn. 

 Dorsal plates of arms very broad. No genital slits 



O. virens (M. Sars) 



Fig. 11] 



-Ophiactis nidarosiensis ; part of oral (a) and dorsal side (6). 

 X 18. (After Th. Mortensen, Scand. Ech.) 



1. Ophiactis Balli (Thom^^OTi). (Fig. 112.) 



(Syn. Ophiocoma Goodsiri Forbes.) 



Disk with rather small scales, those on the oral side much 

 finer. Generally no spines on dorsal side, but on the edge and 

 on the ventral side. Primary plates not distinct. Radial shields 

 small, separated by a wedge of scales. Arms 5. Dorsal plates 



^ Ophiactis profundi may possibly only be a synonym of O. plana 

 Lyman. 



