OF THE MERGUI ARCHIPELAGO. 



93 



arm-plates. Jaw-angles triangular, broad aud short, with a median 

 perforation. Mouth-papillae numerous, eight to an angle, not 

 counting the tentaele-scale on either side. There is one also 

 beneath the teeth, so that there may be from 9 to 11. Tentacles 

 large. 



There are six long rather slender arms. First lower arm-plate 

 small; second plate very much larger, longer than broad, broadest 

 without, outer edge curved outwards, inner edge straight and 

 slightly curved at the sides for the side mouth-shield. Beyond 

 the disk the plates are longer and otherwise retain their outline, 

 but the side arm-plate comes gradually under the arm and dimi- 

 nishes the width of the inner edge. Sides incurved. The large, 

 long, nap-like, curved tentacle-scale abuts against the side of the 

 lower arm-plate. The length of the plates increases over the 

 breadth towards the tip of the arm, and they are separated by 

 the side arm-plates. The tentacle-scale becomes more pointed 

 towards the end of the arm. Upper arm-plates large, heart- 

 shaped, broadest aborally and curved there, narrower orally and 

 roundedly angular there ; sides convex. The side arm-plates come 

 in at the half-arm. Side arm-plates large, flap-like, projecting 

 somewhat near the disk and more flattened to the arm further out, 

 so that the direction of the spines differs ; meeting above and 

 below the arm slightly beyond its outer half. Pour close, cylin- 

 drical, conical, short, stout spines ; their length is less than that 

 of an upper arm-plate and they are longest in mid arm. The 

 upper spine is either the longest or it may be short, the next is 

 the stoutest as a rule, and the others are shorter and more slender. 

 Their surface is plain or minutely jagged. Arms six, high, flat 

 above and below, and nodulated towards the tip. Diameter of 

 disk 4 millim. ; length of arm 18 millim. Colour light brown, 

 without any spots. 



Locality. Owen Island. 



Grenus Ophioco^ta, Agass. 



Ophiocoma scolopexdrixa, Link., sp. ; Mull. 8f Trosch., Syst. 

 Aster, p. 101 (1812). 



Several specimens of this species are in the collection from 

 Mergui; and as there are some interesting points about their varia- 

 tions from the type aud from one another, notice is taken of them. 



In the largest specimen, which has a disk 25 millim. across and 



LINN. JOUEN. — ZOOLOGY, VOL. IXI. 8 



