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Agassiz in Iiis ..Challenger"-Echinoidea p. 70. records A. piilvinata from the 

 Arafura Sea (Chall. St. 188 and 190) and from off Honolulu. As this species is a 

 littoral form and has its home on the pacific coast of America, it was a highly 

 remarkable fact to find it on both sides of the Pacific; its eastern and western 

 representatives were thus separated by the immense, deep tracts of the Pacific 

 Ocean which are uninhabitable for littoral forms. It seemed then a little doubtful 

 to me, whether the Challenger specimens really were A. pulvinata, the more so, as 

 the description given of a j'oung specimen indicates something rather difTerent 

 from the usual features in Astropyga, so that Agassiz is led thereby to the conclusion 

 that „it is very evident from the above that in both these species (A. radiata and 

 pulvinata) we have considerable variation in some of the characters which have 

 thus far been employed to distinguish the two species". 1 have examined all the 

 Challenger-specimens and find that none of them are Astropyga pulvinata. The 

 specimen of 19 mm. diameter (^St. 190) described by Agassiz is Chætodiadema granu- 

 latum (as I had already supposed from the description), and the specimen from 

 St. 188 is the same species. The specimens from Honolulu are either A. radiata 

 or i)erhaps a new species, very nearly related to it. The arrangement of the 

 series of large interambulacral tubercles is as in A. radiata, the series being 

 parallel to the outer edge of the area, not to the median line as in pulvinata. There 

 is a primary tubercle onlj' to every second ambulacral plate. The pedicellariæ are 

 so very similar to those of A. radiata that scarcely a reliable difference can be 

 found therein. The spicules are as in radiata. The abactinal spines are beautifully 

 ringed with narrow redbrown and broad white bands: a few are uniformly redbrown 

 with the point a little darker. The actinal spines are almost or quite white. The 

 coloration of the abactinal side reminds one somewhat of A. pulvinata; the naked, 

 forked band in the interambulacral area is brown, becoming gradually darker 

 towards the median area and is very sharply marked off from the uniformly white 

 median area by an intensely brown border. This beautiful coloration is very 

 well shown in the two specimens, and the third specimen shows distinct traces of 

 it. Perhaps a closer examination will show this form to be a distinct species or 

 a well marked variety of radiata; for the present I must regard it as A. radiata. 

 Unfoi'tunately I have not younger specimens of A. radiata at my disposal; there 

 is only one medium-sized specimen in the Copenhagen-Museum, and it is white, 

 with ringed spines. Now it seems rather remarkable that the younger specimens 

 should be light coloured with ringed spines and the large ones very dark with uniformly 

 dark spines. If young specimens of a uniform dark colour be found besides the 

 light coloured ones, I can scarcely doubt that they will prove to be two distinct 

 species. (The ringed or uniformly coloured spines do not present a reliable 

 character, as both kinds may occur in the same specimen.) Dr. de Meijere has 

 kindly given me information of the colour of the young specimens from the 

 „Siboga"-Expedilion. The specimens from Amboina and Banda have the median 



