ECHINOIDEA. 11. .^ 



and PI. XL\'. Figs. 30— 31 is evidently thi.s form of tridentate pedicellariae. (The figure 31. PI. XLV 

 i.s, otlierwise, not the tip of the blade a.s stated in the explanation of plates — though the expression 

 ..blade is, of course, not used — , but a fragment of the articular surface seen from above). The ophiceph- 

 alous pedicellarice (PI. IX. Fig. 131 have rather elongate valves; the fine teetli along the outer edge 

 of the blade do not continue along the edges down the apophysis, as is the case in Urech. narestanus 

 and the other species related thereto; onh a few coarse serrations arc found along the sides of the 

 apophysis. The basal part is distinctl\- developed, though not reaching the outer widened part of the 

 valve. The arc is distincth- developed on all the valves; the upper end of the stalk is cupshaped. The 

 triphyllous pedicellariae (PI. IX. Fig. 29) are somewhat different from those of the other species of 

 v.Cysfechin7iSf'\ the valves are more elongate and spoon-shaped and more narrowed below than is the 

 case in the other species. 



The descri]-)tion of Cystcch. clypcatns given in the . Challenger -Echini is evidently made after 

 this species. I can only add that the plates are large and very thin, with concentric lines (marks of 

 growth), and that the abactinal pores are simple. The very thick miliary spines, represented in PI. 

 XL\'. Fig. 29 of the Challenger -Echini are found on the anal area of this species. The primary spines 

 are brownish at the base, white in the outer part; the\- are (some of them at least) coarsely serrate 

 in the outer part. 



That the thickplated and the thinplated form represent two ver\' distinct species is beyond 

 doubt; another question is, which of them must keep the name clypeatns, and that is not so easily 

 solved. It is certain that the figures given in the Challenger -Echini represent the thinplated form, 

 and the description likewise is evidently made from this. But on the labels of the thinplated speci- 

 mens (St. 133 and 334) there is a mark of interrogation (though this doubt is, as usual, not mentioned 

 in the text), which seems to indicate that Professor Agassiz liimself regarded the thickplated form 

 as the type of the species, as seems also to be indicated b>" the name clypeatns. However, con.sidering 

 the fact that the species described and figured under that name is really the thinplated form, I think 

 it correct to let this species keep the name Cysfccliiiiiis clypeatns. The thickplated form (St 205) must 

 then have another name; but since its structure is almost quite unknown, so that, in fact, we cannot say 

 to which genus it belongs (probably a new genus), I think it better to let it remain unnamed for the present. 



.Cystechinus'' (Ur echinus) Wyvillii. Four kinds of pedicellariae have been found, viz. globi- 

 ferous, tridentate, ophicephalons and triphyllous. The globiferous pedicellarise (PI. IX. Figs. 3, 5, 24) are 

 essentialh- like those of UrecJi. giganteits, only the blade is shorter and more curved; there is gener- 

 alh- only one tooth on either side of the terminal opening, sometimes, however, there are two on either 

 side. The tridentate pedicellarise occur in two forms: a more slender form, very similar to that of 

 U. )iarcsiaiiHs. and a larger more coarse form (PI. IX. Fig. 17), generally more or less irregular in the 

 lower part of the blade; size up to ca. o-S"'™. These two kinds are, however, not sharply distingui.shed, 

 all transitional forms being found. The figures given in the Challenger -Echinoidea PI. XEII. 13 and 

 XLV. 28 as large-headed (vSpatangoid-like) pedicellarise evident!}- represent the larger form, though 

 a less coar.se specimen than that figured here. The ophicephalons pedicellarise are very like those of 

 U. giganteus; the head of an ophicephalons pedicellaria is represented, though not very clearly, in the 

 figure 27. PI. XLV of the Challenger >-Echini, under the name of a Clypeastroid-like jjedicellaria. 



The Ingolf-Expedition. IV. 2. 7 



