70 



ECHINOIDEA. II. 



the corresponding piates 2, the bi\ial anibulacra thus not being- interrupted b}' the interambulacra 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 piates II. a. 2 and I\". b. 2, som.e- 

 times also IV. b. 3, which are prolonged backwards so as to join the ambulacral piates I. b. i and V. a. i. The 

 interambulacra i and 4 are much prolonged backwards, and the piates i. a. 4 and 4. b. 4 have especially 

 becorae ver\- large; in the abactinal part these interambulacra have a forward direction, thus being in 

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

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

 plate I. a. 3 is abnormalh' divided into two; also the plate dcsignated i. b. 4 is evidently abnormal. 



J bZ 



Fig. 10. Analysis of Part of the test of Poiirfalesia phialc. 

 The plate marked x is probably part of i. a. 3. abnorinally separated off from the latter. 



Whether any of these piates should be interpreted as being compound (in the sense of Lovén's He- 

 teronomy) I do not venture to decide. 



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

 5. a. 6— -8 and b. 7— 9. The apical .system (PI. VII. Fig. 71 is disconnected as in P.Jcfreysi: the genital 

 openings are not developed in the specimens in hånd. The primary tubercles are not serialh' arranged. 

 — The description and figures of spines and ijedicellariæ will be gi\-en in the Report on the Echi- 

 noidea of the German South Polar Expedition, founded on the single, very beautifulh' preserved 

 specimen taken by that Expedition. The specimens from the Ingolf are smaller (8 — 13'nni) and less 

 well preserved, sufficiently well, however, to show that the>' agree in every respect so closely with 

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

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



