35 



of this form of pedicellariæ, under Ihe nanie of „slender long-headed pedicellaria" 

 (Chall. Ech. PI. XLIV. lö); hut that the fig. 5. PI. XLII represents a whole pedicel- 

 laria of the same kind requires a great deal of fancy to understand. De Meijere 

 has found a second form of tridentate pedicellariæ with short hlade and the upper 

 edge of the apophysis serrate (Fig. 280); this form I have not observed. The triphyl- 

 lous pedicellariæ remind one rather much of those of the Echinothuridæ {Astheno- 

 somaLi.); the blade is quite closed in the lower part, the edges meeting and forming 

 a coverplate, the outer end spoonshaped widened; only this widened part of the 

 valves is joining, when the |)edicellaria is closed (PI. V. Fig. 31). The outer edge is 

 finely serrate; de Meijere finds .,hin und wieder kurze Zähnelung" thereupon; I have 

 always found the edge regularly serrate. The stalk is a single smooth rod, widened 

 and irregularly fenestrated at the ends. The ojihicephalous pedicellariæ occur in 

 two very différent forms: a small form, with small head, with or without large 

 glands on the stalk, and another form with large head, without stalkglands; in 

 both of them the head is supported directly on the end of the stalk, there is no 

 neck. The valves of the small form are simple, without meshwork in the blade; 

 the edge is finely serrate, as are the continuations of the apophysis. (Comp, the 

 quite similar form in A. microtaberculaliim, PI. IV. Fig. 12). There is no structural 

 difference between those without and those with stalkglands; the latter may be 

 termed claviform pedicellariæ, being, of course, homologous with the claviform pedi- 

 cellariæ of Diadema etc. The valves of the second form are large, almost triangular 

 with the blade quite filled by a coarse meshwork (PI. III. Fig. 26); the edge is 

 somewhat sinuate, but otherwise thick and smooth ; the point of the blade is bent 

 inwards as a broad hook. The stalk of the ophicephalous pedicellariæ is not a 

 single rod but is rather complicate, irregularly fenestrated, so that it is not distinctly 

 seen to be formed of parallel rods'). The upper end of the stalk in the small form 

 is beautifully cupshaped, that of the large form only thickened and rounded. — 

 De Meijere regards the large ophicephalous form, which he has not found in this 

 species, as a tridentate pedicellaria; I prefer to regard it is as an ophicephalous pedi- 

 cellaria, though its shai)e is rather dilTercnt from the typical ophicephalous form. 

 — It may be mentioned that there is a distinct genital papilla developed. 



This species is recorded in the „Challenger"-Ech. from Cebu and the Ker- 

 madec-Islands, 100—630 fathoms, and from the Atlantic, olf Macio, 1700 fathoms. 

 I was at first doubtful whether the Atlantic specimens would really prove iden- 

 tical with the Pacific ones, both on account of the great distance and of the^great 

 difference in the depth of those localities. I have not, however, been able to find 



') Agassiz (Blake-Echini p. 25.) says that the „shaft" of the „sheathed pedicellariæ" Cm A. Jacobiji 

 and antillanimi consists of „a long, slender radiole, distinctly articulated". This is wrong; it is not 

 articulated only irregularly fenestrated. 



5* 



