g ECHINOIDEA. II. 



the side-edges. In PI. XLII. 24—25, PI. XIJII. Fig. 20 and XLV. Figs. 46-48, 50 of the . Challenger Echini 

 different forms of tridentate pedicellariae are rather well represented, to which figures the reader may be 

 referred. I onh want to call attention to the fact that the apophysis continnes into the edges of the blade 

 as in paradoxa. a notewortln- difference from Jcffrcysi etc. On the other hand it seems rather problem- 

 atic what may be meant by the fignres 21 — 23 of PI. XIJII in that work. In the explanation of the 

 plate they are .said to represent different views of Clypeastroid-like» pedicellarise; this generally means 

 ophicephalous pedicellariae , but tliese figures can scarcely represent the ophicephalous pedicellariie, 

 always so easily recognizable e. g. by the cupshaped upper end of the stalk. It may be suggested that 

 the figure 23 represents a globiferous or perhaps a rostrate pedicellaria; what the two other figures 

 represent I feel unable to give a reasonable suggestion of, the fig. 22 especially seems quite enigmatic. 

 — The miliary spines are of a rather characteristic form (PI. XI. Fig. 38), the outer end is curved and 

 rather thick, almost or quite smooth. — The spicules mainly as in P. paradoxa, q\\\\ a little larger; 

 the ring at the point of the foot is more developed, more like that figiu'ed of P. Jcffrcysi. 



It is well worth noticing that this species agrees rather closely with P. paradoxa (and p/iialc] 

 as regards the tridentate and rostrate pedicellariae, besides in the structure of the test; it can scarcely 

 be doubted that they are rather nearly related, but the shape of the test and the fact that there are 

 two pores iu tiie ambulacral plates I. a. i and V. b. i show P. cariiiata to be the more primitive form. 



Pourtalcsia liispida A. Ag. is stated in the ^^Challeuger Echini (p. 136) to be nearly related to 

 P.Jcffrcysi, whereas later on ( Panamic Deep-Sea Echini » p. 141) Professor Agassiz is incHned to think 

 it so distant from all the other species that it ought to form the t\-pe of a new genus. Unfortunately 

 tlie structure of the plastron was not worked out in the Challenger^ Echini, and there is now no 

 specimen in the British Museum with the plastron completely preserved. P'rom what is preserved it 

 seems, however, almost certain that this species agrees with P.Jcffrcysi in the structure of the plastron. 

 The lal)rum is very small and the two adjoining ambulacral plates very large, especially V. b. i. It 

 niav furliier l)e noticed that the abactinal plates of the odd jiosterior interambulacrum are not .so 

 distinctly alternating as shown in PI. XXII. Fig. 19 of the Challenger > Ech., they are paired as iu 

 /'. Icffrcysi, at least the posterior six i)airs. In the shape of the test 1\ liispida reminds one ratlier 

 much of P. Waiideli, as also the very conspicuous serial arrangement of the priniar\ spines sqmewiiat 

 recalls that species. The primary spines are thorny as in I'. Waiidcli, but much shorter. Oni\ one 

 kind of pedicellariae was foiuid, viz. tridentate. (PI. XI. Fig. 31). They agree with those oi Jcffrcysi and 

 IVandfli. the apophy.sis ending far down on the sides of the blade, another feature speaking iu favour 

 of that relationship. They grow a little larger than in these species. In my preparation of i)edicellari;e 

 of this species I find a pair of globiferous and ophicephalous pedicellariae reseml)liug exactly those of 

 Urrchiuus Wyvillii. Since the s])ecimen examined was from vSt. 147, from which station likewise Urccli. 

 Wyvillii is recorded, I suppose that these pedicellarite really belong to the latter species and liave 

 accidentally got between the spines of Pourt. hispida. 



Pourtalcsia ccratopyga A. Ag. The structure of the bivium of tliis sjiecies is unknown, but judg- 

 ing from the edge of the actinal invagination, as made known by l^oveu, it may well be suggested 

 that it will prove to have the bivial ambulacra uninterrupted as in cariiinta. The plastron is not pre- 

 served in any of the siJecimens in the British Museum. In a fragment from St. 299 I find two pores 



