37 



the inner part, but on every third plale there is a primary tubercle, larger than 

 those of the other plates — in fact the usual arrangement among Diadematidæ 

 prevails here also, the only difference being, that the primary tubercle remains 

 small. — Genital papillæ are found. The spicules as in A. tonsiim. The triden- 

 tate pedicellariæ (PI. III. Fig. 28, PI. V. Fig. 30) are very characteristic; the valves 

 join only for a very short space at the point, the blade is narrow and there is 

 mostly a coarse meshwork filling the bottom almost to the point. There is a well 

 developed neck; length of head c. 1—1-5 mm. The triphyllous pedicellariæ are some- 

 what variable in form, some of them being like those of A. tonsiim, others having the 

 outer part of the blade strongly bent inwards in the middle (PI. IV. Fig. 18). The 

 stalk of the tridentate and triphyllous pedicellariæ is irregularly fenestrated. Of the 

 ophicephalous pedicellariæ I have only seen the claviform ones; but as there is 

 evidently great variation in the occurrence of the large ophicephalous pedicellariæ 

 in other species (e.g. A. tonsiim), it can scarcely be doubted that they will be found 

 in this species too. The valves of the claviform pedicellariæ are small and very 

 simple (PI. IV. Fig. 12). — The sjjecimen from St. 299 is also a true A. microtuber- 

 ciilalam. 



Of the other specimens from the „Challenger" referred to this species those 

 from off Macio and from St. 122 are certainly not A. microtubercnlatiiin. There are 

 no spines on the buccal plates; only in one of the specimens from off Macio I have 

 found a single spine on four of the buccal plates, and of these two were partly 

 transformed into sphæridiæ, looking very much like the figure I have given in my 

 paper on Echinoderms from East Greenland') of transformed buccal spines of 

 Echinus esciilentiis. The pedicellariæ are like those oi A.antillarnm: in fact I think 

 the specimens must be referred to that species. The absence of spines on the buccal 

 plates distinguishes them from A. tonsiim, as does also the size of the ambulacral 

 tubercles. — The specimens from St. 298 I have not seen. 



Aspidodiadema antillanim Ag. The ambulacral tubercles are not equally 

 sized, those on every third plate being a little larger than the others, thus indicating 

 the primary tubercle of the compound ambulacral plates in other Diadematids. This 

 feature is well shown on PI. IX. fig. 6 of the „Blake^- -Echini. (Com^i. A. microiiibercu- 

 latiim); it is no quite regular feature, however, sometimes the tubercles of several 

 plates in succession being ecjually large. The buccal plates are naked, as are also 

 the anal plates in young specimens; in larger specimens the latter are covered with 

 spines. Genital papillæ are developed. Of the pedicellariæ Agassiz has given--some 

 rather bad figures, and the text, stating that „they are either long narrow-headed 

 and long-stemmed, or short-headed and stout-stemmed, or short-stemmed and pyra- 

 midally headed" („Blake"-Echini. p. 2(3), is in no way better. The three usual kinds 

 of pedicellariæ occur. The tridentate and triphyllous pedicellariæ (PI. IV. Fig. 16, 29, 35) 



') Meddelelser om Granland. XXIX. li)();i. p. 7S. Fig. 1-3. 



