78 



ECHINOIDEA. II. 



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

 different forms of tridentate pedicellariæ are rather well represented, to whicli figures the reader mav be 

 referred. I onlv want to call attention to the faet that the apophysis continnes into the edges of the blade 

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

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

 plate they are said to represent different views of ,:Clypeastroid-Hke» pedicellariæ; this generally means 

 ophicephalons pedicellariæ, but these fignres can scarceh" represent the ophicephalous pedicellariæ, 

 always so easily recognizable e. g. b\- the cupshaped upper end of the stalk. It may be snggested that 

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

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

 — The miliar\- spines are of a rather characteristic form (PI. XI. Fig. 38), the outer end is cnrved 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. Jcffrcysi. 



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



as regards the tridentate and rostrate pedicellariæ, 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 faet that there are 



two pores in the anibulacral piates I. a. i and V. b. i show P. cariuata to be the more primitive form. 



l'ourtalcsia hispida A. Ag. is stated in the ^^ Challenger;- Echini (p. 136) to be nearly related to 



P. Jcffrcysi, whereas later on ( Panamic Ueep-Sea Echini » p. 141) Professor Agassiz is inclined to tliink 



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



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



specimen in the IJritish Museum witli the plastron completely preserved. From what is preserved it 



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



The labrum is very small and the two adjoining anibulacral piates very large, especially V. b. i. It 



mav further be noticed that the aljactinal piates of the odd posterior interambulacruni are not so 



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



/'. Jcffrcysi, at least the posterior six pairs. In the shape of the test /'. Iiispida reminds one rather 



much of I\ Waiidcli, as also the very conspicuous serial arrangement of the primar\- spines somewhat 



recalls that species. The primary spines are thorny as in /'. Waiidcli, but much shorter. Onh' one 



kind of pedicellariæ was found, viz. tridentate. (PI. XI. Fig. 31). They agree with those ol Jcffrcysi and 



Waiidcli, the apophysis ending far down on the sides of the blade, another feature speaking in favonr 



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



of this species I find a pair of globiferous and ophicephalous pedicellariæ resembUng exactly those of 



Urcchiiius Wyvillii vSince the specimen examined was from St. 147, from which station likewise Urccli. 



Wyvillii is recorded, I suppose that these pedicellariæ really belong to the latter species and have 



accidentally got between the spines of Pourt. Iiispida. 



Poiirtalcsia ccratopyga A. Ag. The structure of the bivinm of this species is unknown, but judg- 

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

 that it will provc to have the bivial ambulacra uuinterrupted 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 



