ECHINOIDEA. I. 55 



Tetradactylous pedicellariæ have not been observed. Of tridentate pedicellariæ three kinds are found, 

 witli no transitions between them. The first form resembles that in A. fciiestratuiii^ bnt is finer and 

 more slender (PI. XIII. Fig. 22); the head i™'". The second form (PI. XIII. Fig. 10), which corresponds 

 to the second form in A. /cncsfrafniii, is ver}' large, the head 2™'". The blade much involnted; the 

 widened part of the point rather large, coarsely sinnate in the edge. The valves only slightly cnrved, 

 and accordingly the pedicellaria when shnt has a pecnliar lengthened appearance. The third, smallest 

 form is very characteristic, with involnted edge and the onter end widened, withont large cnrves in 

 the edge (but with fine .serrations) (PI. XIII. Fig. 11). Triphyllous pedicellariæ of the same kind as in 

 the other species, only more .slender (PI. XII. Fig. 29). The stalk of the pedicellariæ of the common 

 structure. Spicnles as in A. fciirstratuni^ in two well-separated series to the very point. Well-developed 

 sncking disk. — For this species I propose the name of Aræosoma Belli n. sp. 



Asthenosoinai pcllucidnm A. Ag. Of this species, which is ea.sily recognised as well by its 

 whole habitus, as by its light spines with red bands, Agassiz says (Chall. Ech. p. 87): > Unfortunately, 

 the largest specimens of Astliciiosoina pclluciduiii are so much smaller than the smallest Asfhciiosoiiia 

 coriaceum or the single specimen of Asthciiosoina ttssrlafiii/i , that I am unable so satisfy myself that 

 the present species (Asfhciiosoiiia pcUucidniii) may not be the young of Astliciiosoina coriaceum. In the 

 only species of the group of which the Challenger collected a complete series [Phoriiiosoiiia tciiuc) 

 there was little difficulty in recognising the young as belonging to the adult*. We could scarcely 

 wish to find a more pregnant proof of the difficulty or impossibility of deterinining Echinids withont 

 taking the pedicellariæ into consideration. Asfhciiosoiiia ■ pclluciduiii is so far from being identical 

 witn A. coriaceum or fcssclafiiiii^ that it must form a separate, very well characterized genus, and with 

 reo-ard to the excellent long series of Phoriiiosoiiia^ fciiuc^ there are araong the specimens referred to 

 this species by Agassiz at all events two different genera, but no genuine PhoriiiosoiiiaX 



In A. pclluciduiii three different kinds of pedicellariæ are found, viz. globiferous, tridentate, and 

 triphyllous ones. The globiferous pedicellariæ are of a qnite unique') form (PI. XII. Figs. 8—10, 

 PI. XIII. Figs. 20, 24, 25); they cannot be opened as other pedicellariæ, the three glandular bags are 

 inclosed in a connnon skin, and open in the point, each through a separate pore. The valves are 

 situated between the glandular bags; they are simple rods, slightly bisected in the point, a little 

 hoUow on the in.side, and with a rather strong articular surface below. No apophysis is found, and 

 no muscles seem to pass between the valves, what would not be of much use neither, on account of 

 their being quite wrapped by the common bag of skin; they are far from reaching to the point of the 

 pedicellaria. The tridentate pedicellariæ resemble to a high degree the pedicellaria of Ph. tcnue 

 figured by Agassiz (Chall. Ech. PI. XLII. Fig. 7). The con.struction of the blade, however, is rather 

 different: here only a little developed net of meshes is found, and the apophysis is not prolonged 

 (PI. XIV. Fig. 9), in Ph. tcimc there is a rather well developed net of meshes, and the apophysis 

 continues some way into the blade as a conspicuous, serrate crest. ()nly one form of tridentate pedi- 



■) By a cursorj- examination one might be inclined to couipare them witli the Globiferen > of Centrostephauus longi- 

 spinus described by Hamann (1S4). This, however, cannot be done, at all events not for the present; perhaps the head of 

 these modified globiferous pedicellariæ will show a structure recalling the form described here. But of this, I think, we know 

 nothing. The large glands of the stalk in the globiferous pedicellariæ in Centyosleplianus cannot, of course, be compared 

 with the glands in the head of the pedicellariæ of A. pcltucidum. 



