The Marine Fauna of the Mergui Archipelago. 163 



surrounding the central plate. There are several short spines on the margin 

 of the disc, and a few are scattered over the outer part of the ventral inter- 

 brachial space. The mouth-shields are three-sided, the outer margin 

 semicircular, and the inner two edges almost straight and meeting at a 

 point within. The side mouth-shields are stout and taper from without 

 inwards, where they just meet. 



The under arm-plates are squarish with slightly rounded corners, and have 

 a broad central white line and blue coloured lateral margins. 



Of the seven arm spines the lowest is the smallest and the most 

 characteristic. The tip is bent into a hook, and on this spine, on the same 

 side of it and in the same plane, there are two or three other smaller 

 hooks decreasing in size from above downwards. The other spines have a 

 smooth shaft and thorny club-shaped heads. 



Locality. — St. XXIV., Cat and Kitten Islands, 8 to 22 fathoms, rock, 

 sand and broken shells (one specimen). 



0. martensi has been noted from the Philippines, by Semper ; and from 

 Owen Island, Mergui Archipelago, by Duncan (1882), whose reference to 

 " well-marked radial shields " (p. 97), would seem to indicate that the disc 

 was not covered by skin. 



(9) Ophiothrix stelligera Lyman, 1874. 



Eighteen examples of this species were collected from seven stations. 

 They have a disc -diameter of from 4 to 6 - 5 mm. and an arm-length up to 

 30 mm. While some of the specimens show only stumpy, star-headed spines 

 on the disc, others have in addition a number of elongated spines distributed 

 irregularly. 



In an example from Station XXIV., which, like all the others, has the 

 ventral arm-plates with the characteristic " clean curve, without " (Lyman, 

 1874, p. 237), there appear along the ventral median line of the arms one or 

 two small dark specks (or they may be pits) between each plate. In other 

 respects this specimen is similar to the rest, which agree with the original 

 brief description by Lyman as supplemented by Koehler (1905) in the 

 " Siboga " reports. 



Localities. — St. I., East of Tavoy Island and Port Owen, 4 to 12 fathoms, 

 sand and broken shells and mud (four examples). St. VI., between Grant's 

 Island, Eoss Island and Elphinstone Island, 3 to 7 fathoms, rock and sand or 

 rock and mud (one example). St. XIII., Shore of Maria Island, 8 to 10 fathoms, 

 rock and sand (five examples). St. XXII., Hastings Harbour, St Luke's Island, 

 3 to 20 fathoms and shore, rock and sand (two examples). St. XXIV., Cat 

 and Kitten Islands, 8 to 22 fathoms, rock and sand and broken shells (four 



