ECHINOIDEA. II. r. 



here; it is, however, evidently not very correctly drawn. I have seen nothing resembling the figures 

 PI. XL11I. 10— 1 1 ; they probably represent only small specimens of this kind of tridentate pedicellariae. 

 The second form (Pl.X. Figs. 1,4,24,28,29) is coarser and the form of the blade often somewhat irre- 

 gular; it has generally some very irregular meshwork. This kind of pedicellariae is found on the 

 actinal side, and especially on the peristome, even in the mouth they are quite crowded, reaching 

 some way up the oesophagus; those found here are generally more irregular than those on the out- 

 side of the test (Pl.X. Figs. 28— 29). — It is probably this second form of tridentate pedicellariae which 

 is figured in PI. XLIII. Fig. 12 of the Challenger -Ech. under the name of Clypeastroid-like pedi- 

 cellaria; the valve represented in PI. XLV. Fig. 35 as belonging to this form is certainly that of an 

 ophicephalous pedicellaria, but it seems very unlikely that it can belong to this form; the figure 

 PI. XLIII. 12 does not seem so very bad, as it would be in case the valve did really belong to it — 

 and on the other hand, this coarse form of tridentate pedicellariae is generally invested with a rather 

 thick, brown skin, so that by a superficial examination not much more is seen than the figure cited 

 shows. — The ophicephalous pedicellariae are like those of P. Rathbuni, the valves being low and 

 rather broad. The PL XLY. Fig. 35 of the Challenger -Ech. gives a rather good representation thereof. 

 The figures PL XXXV. 17— iS may perhaps also represent the ophicephalous pedicellariae; thev are 

 however, so crudely made that it is quite useless to speculate 011 what they are meant to represent. 

 — The triphyllous pedicellariae are like those of P. Rathbuni. The supporting rods of the filaments of 

 the actinal tube-feet are like those of Urechinus; spicules I have not seen. The spines evidently deserve 

 to be carefully studied ; my preparations however do not allow me to give more than a few remarks 

 thereon. The only (broken) primary spine I have seen does not agree with the figure and description 

 given by Agassiz, it is curved and finely undulated along the longitudinal ridges. Clubshaped spines 

 are found at the actinostome as in Urech. naresianus. 



To the Urechinida is further referred the genus Calymne. The figures given in the Challenger 

 Report do not allow one to see the real structure of the anterior paired 

 interambulacra; finding that this was an important character for the classi- 

 fication of the Meridosteruata (viz. whether the second plate of these 

 interambulacra is single or double — Comp. below p. 85), I carefully examined 

 the fragments of the type specimens in the British Museum in this regard 

 and found that the first plate is in contact with two of the following plates. 

 The unusual size of the actinal ambulacral plates makes it a little diffi- 

 cult to see the real structure in the poor fragments preserved; but the 



pores of the ambulacral plates are distinct and leave no doubt of the pi S- 1- Part of the actiaal side 



of the test of Calymne relicta. 



morphological value of the plates (Fig. 7). (The figure is made after a 



sketch taken without camera and thus cannot claim to be quite correct as regards the outline of the 



plates; but in the main features it is correct.) 



The apical system is certainly not very correctly given in the Fig. 2. PL XXXIV of the 



Challenger -Ech. The two anterior genital plates with the madreporiteseem to be confluent, not forming 



two (or three) separate plates as in that figure. Of the two posterior genital pores seen in this figure 



