Type Species. Odinia semicoronata Perrier, 1885.

Plate 1

Ophidiaster macknighti n.sp. 1.—Abactinal surface. 2.—Actinal surface.

Photo: M. D. King.

Figs. 5–9.—Odinia novaezelandiae n. sp. 5.—Portion of abactinal surface of disc, showing the raised madreporite, irregularly shaped plates, spines, pedicellariae and papulae. 6.—Crossed pedicellaria. 7.—Portion of genital inflation near the disc, showing the costae and adambulacral spines and pedicellariae. 8.—Portion of arm, beyond the genital inflation, in lateral aspect, showing the intercostal plates. 9.—Portion of arm near the tip, showing the adambulacral plates and the very conspicuous, elongate costal spines.

Odinia novaezelandiae n. sp. (Plate 2, figs. 5-14)

Diagnosis. The disc is small and the single, small madreporite is marginal in position. The 18 arms are long and tapering with conspicuous genital inflations proximally; the adambulacral plates have a distinct series of three or four slender spines and one large subambulacral spine. Crossed pedicellariae are very numerous and of a very characteristic type.

Description. The small, oval, more or less flat disc (about 33 by 24 mm) is paved by a close mesh-work of cruciform or irregularly lobed plates; near the margin these are large and sturdy extending as tongues, separated by smaller plates, onto the actinal surface. There is a covering membrane present which obscures the outlines of the plates and extends for some distance up the spines. Each plate bears from one to four or exceptionally five short (1 to 2 mm long) sturdy spines either spaced or in a compact group, occasionally the spines may almost coalesce completely, only the tips being free; these spines rise from a slightly bulbous base, narrow medially and terminate either in a round head or a number (eight or more) of fine spinelets (Fig. 5). Numerous small crossed pedicellariae (Fig. 6) with very distinctive widely separated jaws occur on the plates and spines of both the arms and actinal surface; in the living animal they are probably embedded in the covering membrane.

Single, small, slender papulae occur in the membranous spaces between the plates of the disc (Fig. 5).

The small (about 3 mm) circular madreporite is distinct, raised, marginal in position and dissected by a number of fine deep, radiating grooves (Fig. 5).

The anus is not apparent; no previous descriptions of other species mention an anus and it seems probable that it is not present in this genus.

Of the 18 long (190 to 200 mm) tapering arms only 7 remain attached to the disc. Between the genital inflation and the disc, the arms are joined laterally to each other for 6 or 7 mm; these areas are paved dorsally by small, irregularly shaped plates bearing from 1 to 3 spines which terminate either in a single, sharp, hyaline tip or more usually in a number (up to 7) of fine, needle-like spinelets, single papulae occur between the plates; along the sides of the arms the plates overlap, there are no papular areas and few spines. Crossed pedicellariae are numerous. Distally the inflated genital region rises steeply, the swelling extending for about 36 mm along each arm; these areas are paved by a close mosaic of small, irregularly lobed intercostal plates between which papulae occur and which bear either one or two blunt-tipped spines; pedicellariae, occurring on the surfaces of the plates are embedded in membrane and probably in life this completely hides the spines. Nine or ten distinct costae or ribs of small, oblong, overlapping plates or ossicles (Fig. 7) are present along the inflation, each rising from about the level of every third adambulacral plate, but they are indistinct for the first 10 or 12 mm of the genital inflation. The costal plates adjacent to page 7the adambulacrals bear from one to three sharp or blunt-tipped spines, proximally these do not exceed 2 or 3 mm in length, but distally, beyond the inflation, they are between 5 and 7 mm long; similar but shorter spines also occur on the intercostal ossicles, giving the area a distinctive and prickly appearance.

One arm, about 16 mm long, is regenerating; there is a distinct genital inflation (about 8 mm long) on which the costal and intercostal plates are crowded and indistinct; distally the lateral spines of the costae are very short with the characteristic crossed pedicellariae. On the actinal surface only the subambulacral spine is obvious, the furrow spines are either absent or one may be present; the small tube feet are biserially arranged.

Beyond the genital inflation the central elements of the costae become rudimentary and finally absent altogether and the arms are paved by narrow, straplike intercostal plates (Fig. 8) which join with similar plates along the mid-dorsal line; the lateral costal plates, with from two to five spines persist. The most dorsal spines are small, between 2 and 4 mm long, the remainder may be up to 10 mm long and are often very close together (Fig. 8); distally they decrease in length and the arm tip terminates in a single sharp spine; all these spines are liberally covered with the characteristic crossed pedicellariae.

There is a marked adoral carina of five to seven adambulacral plates. The hand-like adambulacral plates (Fig. 9) are separated by distinct muscular intervals; within the furrow the distal tip of each plate overlaps the proximal region of the adjacent plate. Each plate bears one prominent, upright subambulacral spine, measuring proximally, between 4 and 5 mm, and distally seldom exceeding 2 mm; these may be blunt-tipped or bifid. Within the groove from two to four small pointed furrow spines form an oblique row; both these and the subambulacral spines are covered with the characteristic crossed pedicellariae which are slightly larger than those on the abactinal surface (Fig. 9). The arrangement and shape of the adambulacral and ambulacral plates is most obvious when the covering membrane is removed from the abactinal surface (Figs. 10 and 11); near the disc the ambulacral plates are large and stout, distally they are considerably smaller and somewhat different in shape.

The tube feet, each with a single ampulla (Figs. 10 and 11) are regularly biserially arranged, with distinct sucking discs.

Each small, fan-shaped mouth plate almost meets with that adjacent to it, thus forming a barrier at the base of the furrow. Each plate bears four or five short, almost conical furrow spines with numerous pedicellariae, these may interlock with spines of neighbouring plates; there are no suboral spines. The first adambulacral plate bears only one slender spine (Fig. 12). A distinct cleavage zone for the arms occurs at the level of the second adambulacral plate.

Figs. 10–13.—Odinia novaezelandiae n. sp. 10.—Dorsal aspect, midway along the arm, with the covering membrane removed. 11.—Dorsal aspect of arm, near the tip; the covering membrance has been removed. 12.—Actinal aspect of arm base and disc showing the fan-shaped oral plates and adjacent adambulacral plates. 13.—Sections of oocytes.

Anatomy. The proximal part of the inflated genital region is packed with the long, much branched ovaries which contain oocytes of varying sizes (Fig. 13). These tubules (Fig. 14) join at a point about 5 or 6 mm from the beginning of the genital inflation and are attached to the ridge of the adambulacral plates, page break

Plate 2

Odinia novaezelandiae n. sp. 1.—Abactinal surface. 2.—Actinal surface.

Photo: H. D. O'Kane.

page 9

Fig. 14.—Odinia novaezelandiae n sp. 14.—Dissection of the arm in the region of the genital inflation, showing the packed pyloric caeca, the much branched ovaries, and the adambulacral and ambulacral plates.

the ducts probably open to the exterior but the opening is not apparent. Fisher (1919, p. 508) reports a similar condition in Odinia magister from Philippines Seas.

The pyloric caeca (Fig. 14) are small, closely packed masses of tubules, these continue for only a short distance beyond the gonadial inflation and are packed with oil globules and connected to a long axial canal suspended from the body-wall by a mesentery.

Colour. In colour photographs of the living animal taken by Mr H. D. O'Kane, the disc and genital inflations are light fawn or grey, becoming orange on the spines and pedicellariae and in the lateral regions; the tube feet are orange-pink and the oral membrane orange.

Discussion. This new species is distinguished by having 18 arms and 3 or 4 adambulacral furrow spines. It is distinct from the only other Southern Hemisphere species, O. australis, by differences in the adambulacral armature and by having only one madreporite, whereas O. australis has four. The present species seems most closely allied to Odinia penichra from the Philippines Seas, but it is distinct in having 18 arms and two or three adambulacral furrow spines, compared with the single spine illustrated by Fisher.

Material Examined. 1 specimen from off Chatham Islands; 43° 52′ S, 175° 20′ E (N.Z. Oceanographic Institute, Wellington, Station No. C 618), 625–690m.

Holotype. In the collection of the Oceanographic Institute, Wellington, N.Z. Holotype Number: 7.