ECHINOIDEA. I. 129 



vn)i Bniiifi Ag., viridix Ag., and iiiacrosfonia (Ltk.). Whethei the last-nanied one is a genuine Echi)io- 

 )iirtra cannot be decided for the present, as onh- naked tests and loose spines are known. The otlier 

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

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

 are to be nientioned. A primår)- tubercle is found on all the ambulacral piates; no ocular plate reaches 

 to the periproct in Ecli. ohlonga and viridis, while in hicuntcr generally one plate, rarely two or none 

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

 all without pedicellariæ. vSpines on the buccal piates. The globiferous pedicellariæ ha\-e one uupaired, 

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

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

 the middle; in E. 7'aii Bnii/ti the globiferous pedicellariæ are very small, but otherwise of the conimon 

 form. The tridentate pedicellariæ are narrowly leaf-shaped with little developed mesh-work (see Re\-. 

 of Ech. Pi. XXVI. Figs. 9, 12 — 13I; in van Brniih' i\\e\ are of a quite different form, short, narrow, 

 a little widened in the point, and the blade quite filled by a complicate me.sh-work (PI. XIX, Fig. 21). 

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

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

 spicules bihamate. 



The genera Urtcrocriifrofus^ with the species ii/ai/alla/iis (Klein) and trigouariiis (Lamk.), and 

 Coloboccntrofns^ with the species af ro fus (L.) and Mcrfciisii Br. are most nearly allied to Ei/iiiion/i'fra, 

 as is commonly supposed; the globiferous pedicellariæ and the spicules are chiefl\- as in this genus. 

 A primar\- tubercle is found on all the ambulacral piates; no ocular plate reaches to the periproct. 

 The buccal membrane with numerous fenestrated piates several of which carry pedicellariæ and small 

 spines as the buccal piates. The gills are in Hctcrocnitrotiis uncommonly well provided with fenes- 

 trated piates some of which even carry (triphyllous) pedicellariæ; rather numerous small bihamate 

 spicules are also found among the fenestrated piates. In Colobocrnfrofiis fewer fenestrated piates are 

 found, but also here they carry triphyllous pedicellariæ. — Onl\- in these two genera I have seen this 

 peculiar feature that pedicellariæ are found on the gills. — In Colohoccutrofus the globiferous pedicel- 

 lariæ 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. Mrrtciisii 

 I have not seen the globiferous pedicellariæ.) Of the tridentate pedicellariæ in Hctcrocciitrofiis 

 Agassiz (Rev. of Ech. p- 665) has the remarkable e.xpressiou that the tridactxle pedicellariæ are of 

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

 figure is given of these pedicellariæ in //. iiiai/iillafi/s (XXVI. Fig. 2). There is a striking difference 

 between the tridentate pedicellariæ in iiiaiiiilfafiis. and frigoiiariiis. In the former (PI. XIX. Fig. 15) the 

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

 valves onl}- join at the point, and are otherwise wide apart; in trigonayiiis the blade is of the connnon 

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

 length. In both of them the edge is \-ery .slighth- serrate, but there are some larger indentations in 

 the narrow part of those of iiiaiiiitldfiis. Perrier (op. cit.) thinks that several Hcf('rocn/fr(d?is-s\)ec\e& 



■) Rech. sur les Péilicellaires etc. PI. VI. 



The Ingoll'-Expedition. IV. i. I7 



