20 



Two large, beautiful specimens were taken at Koh Kahdat, in 4—5 

 fathoms. 



DÖDERLEIN regards A. e/as/ica Studer and A. Freiidenhery i Sarasin as synonyms 

 OÏA. radiata. I must decidedly follow him therein. I have examined in the Berlin- 

 Museum the type specimen of A. elastica and a specimen of A. Freudenbergi with 

 regard to pedicellariæ and spicules and find them quite identical with those 

 of A. radiata. As A. piilvinala Lamk. and deniidata de Meijere differ markedly from 

 radiata in regard to pedicellariæ, one might expect also to find some difference 

 here, if they were really distinct species. The characters pointed out by the 

 authors as distinctive have been shown by Döderlein to be quite unreliable. 

 Evidently they cannot be maintained as distinct species, not to speak of a distinct 

 genus as suggested by Sarasin. To be sure Bell ') maintains A. elastica to be 

 distinct from A. radiata, and he is even right in some way. I have seen his speci- 

 mens of elastica in the British Museum; they are so far from being identical with A. 

 radiata that they are no Astropyga at all, but a species of Micropyga (M. violacea de 

 Meijere, probably). I have not examined the disposition of the pores in these specimens, 

 it is true, but the anchor-shaped spicules in the tubefeet show beyond all doubt that 

 they belong to the genus Micropyga. — Studer says of his A. elastica : „die ganze 

 Schale war mit einer dicken gallertigen Epidermis überzogen" (p. 869). I have not 

 remarked the epidermis in my specimens to be especially jelly-like. — The type 

 specimen of A. /nossa/nfc/ca Peters I have also examined for pedicellariæ and spicules 

 and found them to be identical with those of A. radiata. 



The differences between A. radiata and pulvinata in the structure of the 

 test have been most excellently represented by Döderlein. I may here point out 

 the difference in the pedicellariæ. The tridentate pedicellariæ occur in one form 

 only, all transitional forms being found between the largest and smallest ones. 

 The largest ones found are about 0,8 mm. (head), with a short neck; the smaller ones 

 have a long neck. The blade in the larger ones is mainly of the same form as 

 in A. radiata, but the edge is more irregular (PI. III. Fig. 3). Below there are a 

 few large indentations, the edge being bent somewhat outwards; between these 

 indentations and the outer, well marked portion, where the valves join, the edge 

 shows a large irregular sinuation. There is very little meshwork in the bottom of 

 the blade. The smaller forms are more like those of radiata. The triphyllous 

 pedicellariæ (PI. IV. Fig. 21) are not very different from those of radiata: the holes 

 in the blade are less elongate and the apophysis does not form so distinct a cover- 

 plate. The claviform pedicellariæ and-the stalk of the pedicellariæ are as in radiata. 

 The spicules are like those of radiata, but they are rather numerous in the abac- 

 tinal tubefeet as well. 



■l Kepoit on the EchiiKMkrni.s (other than Ilolothurians) collected by Dr. Willey. Wh.i.ey. Zoolo- 

 gical Results. II. 1899. p. 135. 



