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Echinoderms from Southern New Zealand

Amphiura heraldica sp. nov. (Figures 5 to 7)

Amphiura heraldica sp. nov. (Figures 5 to 7)

  • Dimensions: R, 8·0 mm.; r, 2·9 mm.; ratio R/r, 2·8.
Disc, circular, flattened, its aboral surface covered by scales of various sizes, amongst which the primaries and the radial shields are prominent. The scales partly imbricate and partly interlock. The six primary plates—namely, the dorso-central and the five radials—are large, contiguous, extend from the centre to halfway to the periphery, and shape the pattern of the English heraldic tudor rose. Adjoining the radial primaries, and interradial in position, occur five irregularly pentagonal plates, one to each iuterradius, and evidently also belonging to the primary system, Adjoining the radial distal border of each primary radial plate there are three small scales arranged as a trefoil, the middle leaflet of which is inserted between the proximal ends of the two adjoining radial shields. The radial page 17
Amphiura heraldica sp. nov.

Amphiura heraldica sp. nov.

Fig. 5.—Aboral view. Fig. 6.—Adoral view. Fig. 7.—Lateral view of arm-segment.

Figs. 5 and 7 to scale at left; Fig. 6 to scale at right.

Abbreviations: A, adoral plate. D, upper arm-plate. DC, dorso-central primary plate of disc. G, genital cleft. I, primary interradial plate of disc. L, lateral arm-plate. O, oral shield. PL, oral plate. R, primary radial plate of disc. S, radial shield. TE, tentacle-scale. V, lower arm-plate.

shields are polygonal, about as broad as long, mutually contiguous. The rest of the aboral surface of the disc is covered by rather large plates, smaller, however, than those already mentioned, and disposed in a less regular manner. The adoral surface of the disc is clothed in coarse, imbricating scales. Genital clefts extend to the Second arm-segment. Oral shields subtriangular, with a proximal acute angle and a distal convex base. Adoral plates subtriangular, larger than the oral shields, meeting broadly (or even overlapping) within. Three pairs of oral papillae, one pair infradental, one pair carried on the oral plates, the outermost borne on the adoral plates. All the oral papillae are large, leaf-shaped, and the two inner pairs have pointed tips.

Arms: upper arm-plates as broad as long, subquadrate, each with a convex distal border overlapping upon the next plate, all broadly contiguous. Lateral plates meeting neither above nor below, each bearing four, short, stout, subequal spines. Lower arm-plates similar to upper arm-plates, Save for the first one, which is more elongate. Tentacle-pores large, each having one large elliptical flat page 18 tentacle-scale, which is borne by the corresponding lower arm-plate. The pore itself is excavated within the lateral plate, and does not encroach much upon the margin of the lower plate.

Colour in spirit, white.

Type locality: Discovery station 2733, Chatham Rise, west of Chatham Islands, 30 metres, November 4, 1950; a single specimen.

Holotype: the unique specimen is in the Zoology Museum, Victoria University College.

The species is peculiar (amongst amphiurids) in respect of the large primary plates. The disc presents the aspect of an early post-larval stage, though its size is much larger than expected, and the arms present mature characters. It is, nevertheless, quite possible that this ophiuroid is a juvenile stage of some large species; but its distinctive features forbid our referring it to any known species.