. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 74 ECHINOIDEA. II. pushed far backwards, separated from the small inner plate at the peristome not only by the ambu- lacral plates IV. b. 2—4 and II. a. 2—3, the posterior one of them being much prolonged backwards along the ambulacral plates and I. b. 1, but also by the interambulacral plates 4. a. 4 and 4—5, which join the ambulacral plates V. a. 1 — 2 and I. b. 1—2 for a long way. The plates 1. a. 4 and 4. b. 4 are very much en- larged, and upon the whole all the plates of these interambulacra are unusually lar
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 74 ECHINOIDEA. II. pushed far backwards, separated from the small inner plate at the peristome not only by the ambu- lacral plates IV. b. 2—4 and II. a. 2—3, the posterior one of them being much prolonged backwards along the ambulacral plates and I. b. 1, but also by the interambulacral plates 4. a. 4 and 4—5, which join the ambulacral plates V. a. 1 — 2 and I. b. 1—2 for a long way. The plates 1. a. 4 and 4. b. 4 are very much en- larged, and upon the whole all the plates of these interambulacra are unusually large. As in pliiale these interambulacra are very much bent upon themselves, the median part being near the posterior end, where- as the upper and lower end is at the anterior end of the animal. That the interpretation of the plates given here is correct seems beyond doubt, from a comparison with P. phiale (Fig. 10), in which the interpretation lies quite evident. — The plates of the antero-lateral ambulacra and in- terambulacra are rather small, in accordance with the small size of the «head». The odd anterior am- bulacrum contains ca. 14 pairs of plates; I have been unable to count the number with full certainty. The invagination is comparatively small, but otherwise of the usual form. The peristome is almost round, cov- ered with rather large plates. The mouth is a little below the middle. The apical system is situa- ted near the anterior end; from the outside I was unable to see the limits of the plates in this region. Fig. 13. Analysis of part of the test of Ponrtalesia paradoxa. with any certainty, but from the inside most of them could be distinctly seen (Fig. 14). Probably the plate just behind the large inner prolongation from the madreporic plate will really be divided in two, but I could not distinguish any line there. Also the small innermost plate of the antero-lateral. Please note that these images are extracted from scanned page images that may have b
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