27 



The dental apparatus is very low, but otherwise typically diadeiuatoid, the 

 teeth being unkceled. The auricuhe and their connecting ridges are bent very 

 strongly inwards; the connecting ridge is very high, the auricula; themselves forming 

 only little projecting corners; the opening is rather small, triangular. 



The colour of the abaclinal side of the test is well shown by the beautiful 

 figure given in de Meijere's work (PI. XI. Fig. 101), except that the white tubercles, 

 seen on account of the spines being torn olT, make the figure look a little different 

 from the living, undamaged animal, in which the uniformly brownish spines do 

 not contrast with the colour of the test. The blue spots do not extend below the 

 ambitus; there is a series of large, mostly triangular spots down each side of the 

 interambulacra along the inner side of the outer series of large tubercles, one to 

 each plate, a large spot on each genital plate and some smaller spots irregularly 

 scattered over the whole abactinal side. The actinal side, test and spines, are 

 whitish. 



Of this species a large, beautifully preserved specimen was taken 15 miles 

 W. of Koh Kut, at 30 fathoms, and 4 large, but rather badly preserved specimens 

 were taken 7 miles NW. of Koh si Chang, at 10 fathoms, hi both localities the 

 bottom was soft mud. Further a s])ecimen was found in the Copenhagen Museum, 

 labelled: Gulf of Siam, Salmin 1877. It was determined by Lütken as Astropijga 

 n. sp., but he never gave a description of it. — On the specimen from Koh Kut 

 a small crab was discovered on the spines of the abactinal side and some small 

 Cirripeds were found fixed to the point of some of the actinal spines. 



It is very curious that this large and beautiful Echinid should not have 

 been known previously, though being a littoral form, whose distribution, it might 

 he supposed beforehand, could not be limited to the Gulf of Siam; from the locali- 

 ties recorded by the Siboga-Expedition it may be safely inferred that it is distributed 

 over the whole Malay Archipelago. In fact it has been recorded several times, 

 already, only under other names. De Meijere has shown that the specimens from 

 the Bay of Batavia mentioned by Sluiter (Die Echiniden-Sammlung d. Museums zu 

 Amsterdam p. 68) under the name of Astropijga radiata are really Chcvtodiadenia 

 graiiiilatnm, and I am able to add two other instances. In the Challenger-Echinoidea 

 p. 70 Agassiz describes under the name o( Astropyga puluinata a young specimen of 

 19 mm. diameter (from St. 190), which from the description appears to be a Chœto- 

 diadema; after having examined the specimen in the British Museum I must positively 

 assert it to be a young Cha'todiadema, and further I find the specimen from St^l88 

 (42 mm. in diameter) to be the same species. — Through the kindness of Prof. S. F. 

 Harmer in Cambridge I have been able to examine some Echinids from the Maldive 

 Islands (Collection J. S. Gardiner); I find among them a small specimen of Chœto- 

 diadema granulatum from N. Male, labelled Astropyga sp. juv., evidently one of the 

 specimens mentioned by Bell') as immature' forms of Astropyga in his Report on 

 ') The Fauna and Geography of the Maldive and Laccadive Archipelagos. I. Part. 3. p. 231. 



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