Echinoidea and Asteroidea from Mergui Archipelago. 33 



cases, however, all the spines are more poorly developed, and those of the 

 supero-marginals are not prominent. Two specimens have no central apical 

 spine. The number of pedicellariae which develop varies considerably. In 

 some cases they are numerous on the reticulating bars of the dorsal ossicles 

 up to the base of the lophial spines ; in other cases they are rare even on 

 the supero-marginals. 



There is great variation in the colour of this species when alive. Most 

 individuals are bright red or carmine except for the poriferous areas which 

 are brown or grey, but many examples were noticed of a bright yellow or 

 even orange colour. 



Distributed from Mozambique and Zanzibar to Ceylon. 



14. Pentaceros superbus, Mobius. 



Mobius, Abh. Geb. Naturw. Hamburg, Bd. iv., Abtb., ii. p. 5. 



Locality. — XIV., Bushby Island, 15 to 23 fathoms, sand and rock. 



Two large dried specimens from Bushby Island pearl bank. These 

 remarkably fine specimens are superior to any which I have seen in this 

 country. 



^ = 220 r = 63. Width of arm at base = 70. 



Previously known from Tuticorin and Sumatra. 



15. Pentaceros gracilis (Liifcken). 



Liitken, Yidensk. Medd. (1871), p. 260. Penier, loc. cit., v. p. 62. 

 Localities. — Abundant throughout the Archipelago and Moskos Islands on all 

 pearl banks in 10 to 30 fathoms. 



All the marginals are tuberculated. On the largest specimens the 

 tubercles in the arc between the arms tend to split into two or three or 

 more, especially on the infero-marginals. The lophial tubercles tend to be 

 larger than others in many specimens. Tubercles occur at the corners of 

 all the poriferous areas, especially in larger individuals : in smaller ones they 

 do not all develop. Apical tubercles are specially prominent in smaller 

 specimens : in larger ones other tubercles approximate to them in size. 

 There are generally spines on the apical region, but sometimes only two or 

 three around the anus. 



There are many small valvular pedicellaria?. on the marginals of both 

 series and on the ventral surface. 



In the two largest specimens M = 200 r = 66. i?=146 ?* = 60. 



In life the colour of this animal is orange-red with the tubercles of a 

 brighter orange colour and the poriferous areas greyer. 



vol. xvm. c 



