12 



edge of this outer part has extremely fine serrations, visible only under high magni- 

 fying powers. The neck of this small form is long. On PI. V. Fig. 14, 15 is figured 

 a valve of a tridentate pedicellaria intermediate in size and form between the 

 large and the small kinds. — The triphyllous pedicellariæ (PI. IV. Fig. 26) arc simi- 

 lar to those of the Echinidœ; the apophysis does not form a coverplatc over the 

 lower part of the blade; the edge is cjuite smooth. The neck is long. — The stalk 

 of the tridentate and triphyllous pedicellariæ is mostly very long, up to c. 10 mm., 

 and exceedingly thin, being formed of only a single, somewhat thorny, calcareous 

 rod, or, in the large tridentate pedicellariæ, of two rods, whose thorns unite 

 and form crossbeams between them. At the upper and lower ends, below the ter- 

 minal swelling, the stalk is thicker, consisting of some more irregularly connected 

 rods (PI. IV. Fig. 31, 34.). This structure of the stalk, which has also been observed 

 by i)E Meueue in this species and in Chœtodiadema gramilatum (Op. cit. p. 56), is 

 very characteristic of the Diadematidœ. 



The third kind of pedicellariæ, the ophicephalous or claviform ones, have no 

 head, but three enormous glands on the stalk, which is short and thick, consisting of 

 many rods irregularly connected by crossbeams, but not reaching to the point of the 

 pedicellaria. They are about 1 mm. long. (Comp. Foettinger and de Meuere). De 

 Meijere first pointed out that these claviform pedicellaria^ are probably derived 

 from ophicephalous pedicellariæ (Siboga-Ech. p. 56); that he is right therein, can- 

 not be doubted, I think. The occurrence in Chœtodiadema granulatum of claviform 

 pedicellariæ with a head of undoubted ophicephalous structure together with the 

 common claviform ones without a head proves it beyond doubt. The name „globiferæ" 

 used for these pedicellariæ by Hamann (unfortunately also in „Bronn") must then, 

 as I have said in the „Ingolf"-Echinoidea (p. 169) be rejected on grounds of mor- 

 phology as well as of priority, Foettinger having before Hamann named them „ped. 

 claviformes"; if we want a special name for them, which may be expedient we 

 must call them claviform pedicellariæ, as has rightly been done by de Meijere. 



The sphæridia do not present any peculiar features; they are placed as 

 figured by Loven (Éludes sur les Echinoidées. PI. X. Fig. 89) for Astropyga. 



With regaid to the buccal membrane I must refer to Agassiz (Rev. of Ech. 

 p. 275) and Loven (Echinologica. p. 31 — 32, PI. XII. Fig. 153). Some pedicellariæ 

 (small tridentate and triphyllous ones) are found on the buccal plates and the other 

 plates of the buccal membrane, but mostly in small numbers. According to Loven part 

 of these plates are „studded with verrucules, spinules and forcipes"; probably these 

 „spinules" must be stalks of pedicellariæ; true small spines I have only seen on 

 the buccal plates; I have never found spines on all the buccal plates of the same 

 specimen, and generally there are none at all. It must also be added that the „spicu- 

 les" in the buccal membrane, mentioned by Loven, are the common fenestrated 

 plates. (Of course there are all transitional forms between the larger fenestrated 

 plates and the small irregular „spicules" in the Diadematidœ). The gills are pro- 



