19 



in the lower part of the foot they are generally very scarce. In the abactinal tubefeet 

 no spicules are found, except at the point, where a few spicules of the common 

 form may be seen. The buccal tubefeet, on the other hand, are provided with 

 large, irregular fenestrated plates, curved in accordance to the form of the foot. 

 (They are arranged transversely to the longitudinal axis of the foot). The gills 

 contain the usual irregular spicules, though there are very few in the finer branches. 

 On the side turning towards the test there is a large, thick plate, as is usual in the 

 Diadematids. According to Bell ') the spicules of Astropyga are anchorshaped, like 

 those 0Ï Micropi]ga. This statement must have been caused by a wrong identification 

 of a species of Micropgga as an Astropyga (Comp, below: ^Asiropgga FretidenbergV'); 

 in all the species df Astropyga the spicules are triradiate. 



The pedicellariæ of this species are up to the present time only very incom- 

 petely known. Agassiz (Rev. of Ech. PI. XXIV. Fig. 40) has given a not very good 

 figure of a valve of a Iridentate pedicellaria, and Koehler (Op. cit. ) has figured a clavi- 

 form pedicellaria. Also Lovén has figured the claviform pedicellariæ of Astropyga 

 pulvinata in his „Etudes sur les Echinoidées" PI. X. Fig. 89, without mentioning them, 

 however, in the text. Nothing more is found in the literature on this subject ' — to 

 my knowledge. — The pedicellariæ of ^. radza/a are as in Diadema : tridentate, triphyl- 

 lous and claviform. The tridentate pedicellariæ occur in two forms; the first form, 

 which is found in very difîerent sizes, from c. 05 to more than 2 mm. (length of 

 head), has the blade rather broad and deep, simply leafshaped. (Pi. 111. Fig. 15. PI. V. 

 Fig. 27.) The edge of the blade is coarsely dentate in the lower part; in the outer 

 part, where the valves join, the edge is straight and very finely serrate. In the smaller 

 ones the valves join throughout almost their whole length, in the larger ones they are 

 apart for about - a of their length. At the bottom of the blade there is, in the larger 

 ones a well developed meshwork in continuation with the apophysis; in the small 

 ones, there is only an indication of such a meshwork. The neck is quite short in the 

 larger ones, well developed in the smaller ones. The other, small form of tridentate 

 pedicellariæ (PI. III. Fig. 19) is of the same form as the small ones in Diadema 

 saxatile; the blade is narrow, with the outer end marked ofi" at an angle with the 

 lower part of the edge, which may be coarsely serrate in its whole length or 

 with only a pair of indentations at the lower end. The valves are a little curved 

 and join only at the point. The neck is very long. — The claviform pedicellariæ 

 are of the common form and structure; no true opliicephalous pedicellariæ are 

 found. The triphyllous pedicellariæ (PI. IV. Fig. 17) are very beautiful, the holes- in 

 the outer part of the blade being so very elongate as to pass from the outer edge 

 more than half way down. The apophysis forms a little coverplate over the lower 

 part of the blade. The outer edge is smooth. The stalk of the pedicellariæ is 

 as in Diadema. 



') Note on the spicules found in tiie ambulacra! tubes of the regular Echinoidea. Journ. R. Microsc. 

 Soc. 2 Ser. II. 1882. p. 298. 



3* 



