OF THE MERGUT ARCHIPELAGO. 



103 



Geuus Ophiocnemis, Mull. Sf Trosch., Syst. Aster. 184)2, p. 87 ; 

 Lyman, ' Challenger' Report, p. 228. 



Ophiocxemis marmorata, Link., sp., Mull. Sf Trosch. op. cit. 

 p. 87. 



The genus Ophiocnemis was insufficiently diagnosed by Miiller 

 and Troschel, and the amended definition of Lyman appears to be 

 excellent with a doubtful exception. The lower part of the 

 iuterbrachia is quite naked according to the first-mentioned 

 authors, and scaled according to Lyman. In a specimen of 

 O. marmorata from the Mergui Archipelago the skin is certainly 

 naked and plain. The anatomy of the arms given by Lyman is 

 as remarkable as correct, and the specimen I have examined 

 has the peculiar characters given on Lyman's plate xlii. fig. 15. 



There is no drawiug of Ophiocnemis marmorata, Mull, and 

 Trosch., and their definition is very short. I have therefore 

 considered the diagnosis and allowed for the variation of such 

 forms, and venture to suggest some few alterations. 



The nodular stumps on the skin between the radial shields are 

 not on visible scales, aud they crowd the interbrachial margin, 

 some being on the outer edge of the radial shields. They also 

 crowd in the centre of the disk. Skin plain below. Generative 

 scale large, broad, and arched below where free. A forked 

 genital process on the aboral side of the mouth-shield. Side 

 mouth-shields placed orally to the long diameter (from side to 

 side) of the mouth-shields. First lower arm-plate very small. 

 Beyond the disk the lower arm-plates are broader than long, in- 

 curved orally and aborally, longest at the sides, and slightly 

 incurved there. They increase in length towards the tip. Upper 

 arm-plates much broader than long, at least four times as broad 

 as long, arched and semi-keeled near the end of the arm, edges 

 within and without either slightly curved or straight. Tentacular 

 opening well at the side of the arm in mid-arm ; a very small 

 tentacle-scale on the edge of the side arm-plate. Usually four 

 spines, small, cylindro-conical, not sharp, striated, aud not hollow, 

 only less dense in the centre, banded with colour ; dull white, 

 opaque, and microscopically spinulose. The first becomes a glassy 

 bifid hook at mid-arm ; the fourth varies in size, and the third 

 from the lower arm is the largest. Diameter of disk 13 million. : 

 length of arm 70 millim. Colour in alcohol generally brownish 

 green with splashes of white, and dots, lines, and splashes of dark 



