198 ECHINODERMS OF THE BRITISH ISLES 



Colour ill life not known. Reaches a size of ca. 7 mm. diameter 

 of disk. Arms ca. four times that length. It appears that the 

 arms and spines are covered with a fairly thick skin. 



Development unknown. It appears to live on corals or the 

 like, to which it is able to cling by means of its arms, which can 

 be rolled in ventrally, as in several other Ophiacanthids. 



In British seas this species has been found at 51° 26' N., 

 11° 45' W., 990 m., 22, v. 1914, S.R. (50 m. S.S.W. of Skellig's, 

 Co. Kerry). (Not recorded previously.) It is elsewhere known 

 from off the Azores, 1250 m. (" Princesse Alice "). Also from 

 the West Indies it is recorded (" Albatross "), but it may perhaps 

 hot be quite indubitable whether it is really this same species. 



V. Family Ophiactidje 



Disk often with spines or granules, which do not, as a rule, 

 conceal the scales. Mouth papillae usually not contiguous with 

 the infradental papillae. A single series of square teeth, no tooth 

 papillae. Second pair of tube-feet inside the mouth edge. Spines 

 short, outstanding. Genital organs in one large mass at each 

 bursal slit. 



Three genera known from the British seas, but a fourth is 

 likely to be represented there also, viz. Amphiactis Matsumoto, 

 with the species A. duplicata (Lym.) (Syn. Amphiura, Ophiactis 

 duplicata Lym.), known from the Bay of Biscay, off the Azores 

 and Cape Verde, 628-2178 m. ; it is elsewhere known from the 

 West Indies, and also widely distributed over the Pacific (ca. 135- 

 2870 m.). 



Key to the genera oj Ophiactidoe linown Jrom or likely to 

 occur in the British seas. 



1. No genital slits^ .... 2. Ophiopus Ljungm. 

 Genital slits present ....... 2 



2. Dorsal plates of arms each surrounded by a circle of small plates 



3. Ophiopholis INIull. and Trosch. 

 Dorsal plates of arms not surrounded by small plates . . 3 



3. One or two mouth papillae on each side of jaw, not contiguous 



with the infradental papilla . . .1. Ophiactis Liitken 



Four to five papilla? on each side of jaw, contiguous with the infra- 

 dental papilla^ .... Ainphiactis Matsumoto. 



^ The Mediterranean species, Ophiactis virens (M. Sars), also lacks the 

 genital slits. It is at once distinguished from the 5-armed Ophiopus 

 by having 6-7 arms, and by being self - dividing, half the disk and the 

 corresponding arms being usually about to regenerate. 



2 This genus is otherwise usually referred to the family Amphilepidae, 

 but, in the opinion of the present author, it undoubtedly belongs to the 

 Ophiactidse. 



