78 



ECHINOIDEA. II. 



the side-edges. In PI. XIJI. 24—25, PL XL/Ill. 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 only want to call attention to the fact that the apophysis continues into the edges of the blade 

 as in paradoxa, a noteworthy difference from Jeffreysi etc. On the other hand it seems rather problem- 

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

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

 ophicephalous jaedicellarise , but these figures can scarcely represent the ophicephalous pedicellarke, 

 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, only a little larger; 

 the ring at the point of the foot is more developed, more like that figured of P. Jeffreys!. 



It is well worth noticing that this species agrees rather closely with P. paradoxa (and phiale) 

 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 in the ambulacral plates I. a. 1 and V. b. 1 show P. carinata to be the more primitive form. 



Pourtalesia hispida A. Ag. is stated in the Challenger- Echini (p. 136) to be nearly related to 

 P. Jeffreysi, whereas later on ( Panamic Deep-Sea Echini* p. 141) Professor Agassiz is inclined to think 

 it so distant from all the other species that it ought to form the type of a new genus. Unfortunately 

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

 specimen in the British Museum with the plastron completely preserved. From what is preserved it 

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

 The labrum is very small and the two adjoining ambulacral plates very large, especially V. b. 1. It 

 may further be noticed that the abactiual plates of the odd posterior interambulacrum are not so 

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

 /'. feffreysi, at least the posterior six pairs. In the shape of the test P. kispida reminds one rather 

 much of P. Wan deli, as also the very conspicuous serial arrangement of the primary spines somewhat 

 recalls that species. The primary spines are thorny as in P. Waudeli, but much shorter. Only one 

 kind of pedicellariae was found, viz. tridentate. (PI. XI. Fig. 31). They agree with those of Jeffreysi and 

 Wan deli, the apophysis ending far down on the sides of the blade, another feature speaking in favour 

 of that relationship. They grow a little larger than in these species. In my preparation of pedicellariae 

 of this species I find a pair of globiferous and ophicephalous pedicellariae resembling exactly those of 

 Ur echinus Wyvillii. Since the specimen examined was from St. 147, from which station likewise Urech. 

 II 'xvillii is recorded, I suppose that these pedicellariae really belong to the latter species and have 

 accidentally got between the spines of Pourt. hispida. 



Pourtalesia ceratopyga A. Ag. The structure of the bivium of this species is unknown, but judg- 

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

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

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



