154 '£ ransactions. 



proximo-lateral angles are bevelled off. The length of the plate is about 

 ecjnal to the breadth of the distal margin. 



The side arm-plates just appear dorsally and ventrally. 



There are 2 tentacle-scales. 



The arm-spines are usually 4, over the greater part of the arm, but near 

 the base may be 5 or even 6, while in the distal portion the number sinks 

 to 3. The spines are flattened, smooth, bluntly truncated ; the upper two 

 are shorter and broader than the lower two. 



In one individual I noted that for two-thirds of the arm there are 3 

 spines, and 4 nearer the base ; the 3 are subequal, but the middle one is 

 slightly the longer. Towards the base the uppermost (the 4th) is broader, 

 shorter, and flatter, and truncated. The upper spine is equal in length to 

 about 2 upper plates ; the lowest to nearly 2| plates. 



Colour. — The colour in alcohol is very dark brown, nearly black, with many 

 small pale spots (or, rather, dots), more or less circular, closely set, rather 

 more densely and of larger size near the centre, and often disappearing 

 towards the base of the arms. They are fewer over the adradials, especially 

 along the middle of each, so that here there is a linear dark space. 

 The arms are sometimes neither spotted nor banded, except towards the 

 tips. The upper arm-plates are almost black, but in one individual the 

 arms are banded. The arrangement is as follows : A few of the plates at 

 the base of the arm are marked with a central cream-coloured oval spot, 

 larger or smaller, at irregular intervals, but generally 2 or 3 such plates occur 

 consecutively. Further away from the disc groups of 2 or 3 plates may 

 be nearly wholly of this creamish tint, separated by more or fewer dark 

 plates. Still nearer the tip groups of 3 or 4 plates are marbled with cream, 

 and the intervening ones are grey, with dark margins, so that the ends of 

 the arms are crossed by pale and darker bands. The actinal interbrachial 

 areas are similar to the actinal surface, but the spots are larger and closer, 

 so that this region appears paler, and there results a dark network on a 

 pale ground. The orals and side mouth-plates are dark brown, but the 

 madreporite is cream-coloured. The under arm-plates are pale brown, but 

 close to the disc are cream. Some of the spines have a pale streak along 

 the upper and lower margins. 



Locality. — Coral Bay ; in mud, under stones. 



Distribution. — Lord Howe Island (Clark, 1909), Philippines, Pelew 

 Islands (Lyman, 1874), Amboyna and New Guinea (Clark. 1908), Kingsmill 

 Islands (Lyman), Sandwich Islands (Lyman, 0. insularia). 



Ophiothrix oliveri sp. nov. Figs. 14-17. 



Material : Three specimens. 



Dimensions. — Diameter of disc, 14 mm. ; length of arm, about 82 inm. 

 therefore the arm is about six times the disc-diameter. 



General Colour. — Violet, with paler uuder-surface : when in alcohol, very 

 dark : when dried, much paler. 



The disc is pentagonal, with excavated interradial edges when dried, 

 but bulging here when in alcohol. 



The abactinal surface is covered with a thin skin, strengthened by small 

 conical granules, which when dried are seen to be glassy spinules terminated 

 in 3 or 4 (rarely 6) points, the length of the spine being about three tunes its 

 breadth. 



