FXHINOIDKA. I. 129 



i<(Vi liriDiti Ag., viridis Ag., and iiiacrosloiiia (Ltk.). \\'ht:tlici the last-named one is a genuine Ecliino- 

 i/it/ni cannot be decided for the present, as onh' naked tests and loose spines are known. The other 

 species agree in the main features, also with regard to pedicellarice and spicules; so there is no reason 

 to enter into details with regard to the separate species, only a few features characteristic of the genus 

 are to be mentioned. A primary tubercle is found on all the ambulacral plates; no ocular plate reaches 

 to the periproct in Ech. oblouga and viridis, while in InciDitcr generally one plate, rarely two or none 

 at all reach to it. The buccal membrane contains numerous large, but fine fenestrated plates, almost 

 all without pedicellarise. Spines on the buccal plates. The globiferons pedicellarise have one unpaired, 

 strong lateral tooth, as Perrier has pointed out, and he has figured it in an excellent manner'). There 

 is no neck; the stalk is compact. In E. oblouga is found the peculiarity that the stalk has a joint in 

 the middle; in E.vanBrunfi the globiferons pedicellarise are very small, but otherwise of the common 

 form. The tridentate pedicellaricc are narrowh' leaf-shaped with little developed mesh-work (see Rev. 

 of Ech. PL XX\'I. Fig.s. 9, 12 — 13); in va)i Bniiifi they are of a quite different form, short, narrow, 

 a little widened in the point, and the blade quite filled b\- a complicate mesh-work |P1. XIX, iMg. 21). 

 The ophicephalous pedicellaricC with a rather strong mesh-work, a little different in form, although 

 upon the whole of the common structure; the triphyllous pedicellarije of the common form. The 

 spicules bihamate. 



The genera Heterocentrotns, with the species rnamillahts (Klein) and trigonarius (Lamk.), and 

 Coloboccnirotits, with the species atratiis (L.) and Jlfrrfcnsii Br. are most nearly allied to Echino/i/e'lra, 

 as is commonly supposed; the globiferons pedicellarise and the spicules are chiefh- as in this genu.s. 

 A primary tubercle is found on all the ambulacral plates; no ocular plate reaches to the periproct. 

 The buccal membrane with numerous fenestrated plates several of which carry j^edicellarite and small 

 spines as the buccal plates. The gills are in Hctcrocciiirotiis uncommonh- well provided with fenes- 

 trated plates some of which even carry (triphyllous) pedicellarise; rather numerous small bihamate 

 spicules are also found among the fenestrated plates. In Colobocoifrofits fewer fenestrated plates arc 

 found, but also here they carr\' triphyllous pedicellarise. — C)nl\ in these two genera I have seen this 

 peculiar feature that pedicellarise are found on the gills. — In Colohocoitrotits the globiferons pedicel- 

 larise are quite small and placed quite down among the flat spines on the abactinal side; the edges 

 of the blade not connected b>- cross-beams (PL XIX. Fig. 5). The stalk is curved. (In C. Mcrtcnsii 

 I have not seen the globiferons pedicellaria;.) Of the tridentate pedicellaria; in Heteroccntrotus 

 Agassiz (Rev. of Ech. p. 665) has the remarkable expression that the tridactyle pedicellariae are of 

 the type called trifoliate . I do not understand the sense of this expression; otherwise a rather good 

 figure is given of these pedicellarise in //. niainiUatus (XX\'I. Fig. 2). There is a striking difference 

 between the tridentate pedicellarise in ii/aii/i//afiis and frigoiiariiis. In the former (PL XIX. Fig. 151 the 

 blade is narrow in the lower part, widened at the point, with a pair of rather projecting corners; the 

 valves onh' join at the point, and are otherwise wide apart; in frigoiiariiis the blade is of the common 

 leaf-shape (PL XIX. Fig. 35), with no widening at the point, and the valves join through their whole 

 length. In both of them the edge is very slightly serrate, but there are some larger indentations in 

 the narrow part of those of maniillafiis. Perrier (op. cit.) thinks that several Hetcroccntrotus-'A^t.c\&^ 



') Rech. sur les Pedicellaires etc. PI. VI. 



The Ingolf-Expedition. IV. i. I7 



