^o 



ECHIXOIDEA. II. 



the corresponding plates 2, the bivial ambulacra thus not being interrupted by the interainbulacra i 

 and 4. The inner plate of these interambulacra is small, but distinct, at the edge of the in\agination 

 it is separated from the corresponding second plate b\ the ambulacral plates II. a. 2 and I\". b. 2, some- 

 times also IV. b. 3, which are prolonged backwards so as to join the ambulacral plates Lb. i and \'. a. i. The 

 interambulacra i and 4 are much prolonged backwards, and the plates i. a. 4 and 4. b. 4 have especialh' 

 become very large; in the abactiual part these interambulacra have a forward direction, thus being in 

 some \va\' bent upon themselves (Fig. 10) — a feature which is carried to the extreme in P. paradoxa 

 (see Fig. 13. p. 74). In the interambulacrum i in the specimen from which the Fig. 10 was made the 

 plate I. a. 3 is abnormally divided into two; also the plate designated i. b. 4 is evident!}- abnormal. 



i bZ 



V\%. 10. .Viialysis of Part of the test of Pourtalesia phiale. 

 The plate marked x is probably ])art of i. a. 3, abnormally .separated off from the latter. 



Whether any of these plates .should be interpreted as being compound (in the sense of Loven's He- 

 teronouiyi I do not venture to decide. 



The periproct is not sunken; it is surrounded b\- three epiprcctal plates on each side, viz. 

 5. a. 6— 8 and b. 7— 9. The apical .system (I'l. \'II. Fig. 7I is di.scounected as in P. Jcffrcysi; the genital 

 openings are not developed in the .specimens in hand. The jnimarx- tubercles are not serially arranged. 

 — The description and figures of spines' and pedicellari;e will be given in the Report on the Echi- 

 noidea of the Ck-rman vSouth Polar Expedition, founded on the single, very beautifulh- preserved 

 specimen taken by that Expedition. The specimens froui the Ingolf are smaller (S— 13""") and less 

 well preserved, sufficiently well, however, to 'show that the>- agree in ever\- respect so clo.sel>- with 

 that from the Antarctic Sea that it is quite out of the (juestion to separate them as a distinct species. 

 The question whether the antarctic species described in the Challenger -Report as P. pliialc is really 



