Echinoderms from Southern New Zealand
Ophiomyxa M. & T., 1842
Ophiomyxa brevirima H. L. Clark. 1915
- Alert station 20, three specimens.
Disc dark purple-brown, arms banded with alternating 3 mm. bars of fawn and chocolate, light fawn below.
Ophiomyxa duskiensis Fell, 1947
- Alert station 13, about twenty specimens; station 22, one specimen; station 23, four specimens.
- New Golden Hind stations: NGH 2, three specimens; NGH 25, two specimens; MGH 41a, three specimens; NGH 57a, two specimens (type locality).
The New Golden Hind material has already been described (Fell, 1947). The Alert material, like the former, is uniformly small. The colour in life can now be stated—disc dark purple-brown, dark brown bands on the arm, in two shades of brown, turning dark grey in spirit.
Astrobrachion Doederlein, 1927
Astrobrachion constrictum (Farquhar. 190)
- New Golden Hind station NGH 64a, two specimens.
- Alert station 35, one fragmented specimen.
- Off Westland, 20 miles west of Hokitika, 216 fathoms, on branching coral; coll. H. W. Wellman; four specimens.
One of the New Golden Hind specimens is a uniform purplish-brown, save on the under-sides of the arms, which are paler. It is tightly coiled round an anti-patharian coral (Aphanipathes sp., det F. M. Ralph). The other six specimens are of a variegated coloration, the aboral surface of the disc and the upper and lateral surfaces of the arms are creamy white; the adoral side is purplish-brown.
Astrotoma Lyman, 1875
Astrotoma waitei Benham, 1909
- Ten miles south of Cape Campbell, 40 to 50 fathoms, March, 1947, entangled in trawl-net; coll. F. Abernethy; five specimens.
- Also same locality, 30 to 70 fathoms, February, 1952; J. A. F. Garrick; two specimens.
- Off Westland, 20 miles west of Hokitika, 216 fathoms, on branching coral: coll. H. W. Wellman; one specimen.
In life, this species is a bright lemon-yellow. The creamy white colour mentioned by Benham is assumed after preservation. Its movements are slow and deliberate, and comprise mostly just coiling and uncoiling the arms in the vertical plane.
The eggs are very large and yolky, and range in size from 60μ to 1,00μ across —indicating direct development, The species may perhaps protect the brood, as page 14I find in one Cook Strait specimen a cluster of eggs in a layer one-deep on the fourth, fifth, and sixth segments of one arm.
The number of arm-spines and their arrangement varies somewhat more than Benham indicates in his original description. Each arm-segment bears on either side from eight to ten short, cylindrical, blunt spines. The spines each terminate in a tuft of glassy spicules. In the outermost quarter of the arm, the spines decrease gradually in number till only one or two remain; the outer (that is. morphologically upper) spines of the segments are the ones that persist to the end of the arm.
Ophiacantha M. & T., 1942
Ophiacantha vilis Mrtsn., 1924
- Off Cape Campbell, 50 fathoms, 1947; coll. F. Abernethy; one specimen.
The species has hitherto been known only from one record, that of the type material, which was taken in Cook Strait from 20 fathoms. That its range extends upwards to include the sublittoral region of the continental shelf is now evident: apparently, however, it is rare, since only one specimen was taken out of hundreds of other echinoderms trawled in the same area at the same time.
The specimen shows little sign of the outer lobe of the oral shield mentioned by Mortensen (1924), but in other respects it agrees. The species reaches a larger size than was hitherto supposed. In the present case, the radius of the disc is 3·5 mm., the major radius ca. 30 mm., giving the ratio R/r 8·5; thus the proportions noted by Mortensen are retained.
Amphiura Forbes, 1842
Amphiura magellanica Ljungman, 1866
- Alert station 13, seven individuals.
- Off Cape Campbell, 50 fathoms, April 4, 1947; coll. F. Abernethy; five individuals.
In fresh material of New Zealand examples of this species, the colour seems relatively invariable—the disc is grey above, cream below, the arms being entirely cream-coloured. In the field, therefore, it provides a useful diagnostic feature for separating the species from the very similar following one, where brilliant shades of various colours occur, often with banding on the arms.
In spirit material, it may be noted that in adult specimens of Amphiura magellicana the disc is usually tumid above, on account of the presence of embryos in the hursae—an additional difference to those already cited by Mortensen (1924) as distinguishing it from the following nearly-related form.
Amphiura spinipes Mrtsn., 1924
- Alert stations; 4, three specimens; 13, five specimens; 14, one individual; 20, about forty specimens.
- Lochlan station 367/51, one specimen.
Amphiura spinipes is extraordinarily variable in respect to its coloration, even within populations of relatively restricted area—for example, Alert station 20 (Paterson Inlet, Stewart Island). On preliminary macroscopic sorting of the collection from the latter station, four distinct lots were isolated, on account of colour differences, which afterwards proved to be all of this species. Following are some of the major colour variants noted:—
|(a)||Purple-brown disc and arms—ten individuals from station 20.|
|(b)||Pinkish-fawn above, arms pale fawn below—about twenty individuals from station 20.|
|(c)||Grey, the arms banded with narrow black bars at 2 mm. intervals—one individual from station 4.|
|(d)||Disc dark fawn, arms brilliant orange-vermilion—about twelve individuals from stations 13 and 20.|
|(e)||Disc brownish-orange, arms fawn, with narrow black bands at 2 mm. intervals—two specimens from station 20.|
Amphiura rosea Farquhar, 1894
- Alert stations: 1, six specimens; 3, five young individuals; 6, three individuals.
In the present instance, all material was in spirit before it was examined, so the colours were not noted. Specimens from Alert station 3 are of typical form, but small. Those from station 1 have the radial shields separated by more scales than in the case of Farquhar's type.
Amphiura hinemoae Mrtsn., 1924
- Station NGH 64A, one specimen.
- Alert station 14, ten specimens.
Colour—hitherto unknown from fresh material—pale pink or orange, the disc naked below, the primaries prominently pigmented with grey spots.
The type locality—and, indeed, hitherto only known one—is White Island, 55 fathoms. Thus, again, as in the case of Peronella hinemoae, the southern range of the species is extended by some seven hundred miles, yet no occurrences are known in the intervening waters.
Amphiura amokurae Mrtsn., 1924
- Paterson Inlet, Stewart Island, intertidal, under stones on seaward side of Point Anglem, January, 1951; coll. B. M. Bary; a single specimen.
The species appears to be nowhere common, though isolated instances establish its presence throughout New Zealand from North Cape to Auckland Islands. Only one specimen was obtained by the Cape Expedition (at Auckland Islands).
Amphiura alba Mrtsn., 1924
- New Golden Hind stations: 44, one specimen; 2, two young specimens. Alert stations: 18, two specimens; 20, one specimen.
The above specimens agree with A. alba in having one triangular tentacle-scale, no disc spines, the oral side of the disc completely scaled, spearhead-shaped oral shields, five or six pointed arm-spines, and the outer oral papilla large, flattened, and pointed distally. On the other hand, the six primary plates of the upper side of the disc are quite distinct—of rounded form—each separated from its fellows by smaller disc-scales. In Mortensen's type (from Colville Channel, 35 fathoms), the primaries are said to be "not very distinct." The difference, however, may be due only to age.
We have here yet another instance of a northern New Zealand species occurring seven hundred miles to the southward without known intervening records.
Amphiura abernethyi Fell, 1951
- Alert stations: 10, six specimens; 26, one specimen.
These specimens are all only some two-thirds as large as the type material (from Cape Campbell). They are therefore more directly comparable with the related A. norae. Also, the number of mosaic platelets between the radial shields (about 18 to 20) is smaller than in the type A. abernethyi, though still considerably exceeding the corresponding number (5 to 7) in A. norae. The spacing between the radial shields is not so great in the present material as it is in the type, again a feature reminiscent of A. norae. It would not be surprising if eventually it should be found that A. abernethyi and A. norae are the two limiting forms of a cline.
- Dimensions: R, 8·0 mm.; r, 2·9 mm.; ratio R/r, 2·8.
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.
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.
Amphioplus Verrill, 1899
Dimensions: r, 2·5 mm., the arms broken in the type, but evidently exceeding the minor radius in length by ca. seven times.
Amphioplus longirima sp. nov.
Fig. 8.—Aboral view. Fig, 9.—Adoral view. Fig, 10.—Lateral view of arm-segment. All to scale shown.
Abbreviations: A, adoral plate. D, upper arm-plate. DC, dorso-central primary plate of disc G, genital cleft. L, lateral arm-plate. O, oral shield. S, radial shield. V, lower arm-plate.
Arms: upper arm-plates broader than long, subtriangular, with a broad distal convex border which overlaps the proximal angle of the succeeding plate, save in the first upper plate, where the proximal obtuse angle is exposed. Lateral plates meet neither above nor below, save in the case of the segment which bears the first upper arm-plate (segment five when counted from below); in this case the lateral plates meet in the midline above. Lateral plates each bearing on the basal arm-segments four similar, stout, short spines; on the more distal segments, three spines only. Lower arm-plates subquadrate, with concave distal borders and lateral borders emarginated by the tentacle-pores; neighbouring plates contiguous over most of their width. Tentacle-pores large, having two similar leaf-shaped tentacle-scales on the inner side, both scales being carried, therefore, by the corresponding lower arm-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.
This, only the second species of Amphioplus to be discovered in New Zealand waters, appears to be more closely related to its New Zealand congener A. basilicus, than to any other Pacific or Antarctic form. It can, however, be easily distinguished from A. basilicus by the following: (1) the long genital clefts (to which the specific name refers)—these reach to near the ambitus, whereas in A. basilicus they do not pass beyond the first arm-segment; (2) the oral shields are spearhead-shaped, whereas they are triangular in A. basilicus; (3) the radial shields are somewhat larger and more widely separated. Of the six known Australian species, only A. stemspis and A. didymus seem at all comparable; but the former is distinguished by its long, slender, radial shields, the latter by its larger inner tentacle-scale.
Amphipholis Ljungman, 1867
Amphipholis squamata (Delle Chiaje, 1828)
- Alert station 12, one specimen.
- Also Island Bay Shelf, ca. 10 fathoms, July, 1950; C. A. Fleming; one specimen.
Ctenamphiura Verrill, 1899.
Ctenamphiura dawbini Fell, 1952 (Figures 11 to 14)
- Dimensions: R, 60 mm.; r, 6 mm.; ratio R/r, 10.
Disc: rounded-pentagonal, constricted at the interradii, tumid, robust Aboral surface covered by a coarse, uneven mosaic of lumpy, thick plates, in the manner of cobblestones, none imbricating, and of smaller size in the interradii. No primary plates. Radial shields longer than broad, pearseed-shaped, separated by a wedge of about six mosaic plates; extending from near the periphery to about one-third of the distance to the centre. Adoral surface of the disc naked, save at the sub-ambital border, and save for scales bordering the genital clefts. The subambital plates are uneven, thick, and lumpy like those above. The genital clefts extend to the fifth arm-segment. The oral shields are large, spearhead-shaped, longer than broad, with an obtuse proximal angle; their distal borders abut upon the outer genital scales, their lateral borders rest upon the first lateral arm-plates, their proximal borders alone adjoin the adoral plates. Adoral plates triangular, small, meeting neither within nor without. Three pairs of oral papillae; an infradental pair, flattened, scale-like, large, placed vertically upon the torus, and hence viewed end-on and so appearing smaller than in reality; an apparent outer pair, which, however, are really an intermediate pair, scale-like, very large, rounded, carried by the adoral plates; and an outermost spiniform pair, long, carried on the adoral plates, but reflexed within the oral cleft so as to be partly hidden by the large and apparent outer papillae.
Ctenamphiura dawbini sp. nov.
Fig. 11.—Proximal half of arm viewed obliquely, mainly from below. Fig. 12.—Fig. 13.—Portion of arm, viewed from above at a point where the arm is downwardly flexed, exposing the arm-plates more fully than in Fig. 12. Fig. 14.—Adoral view.
Fig. 11 to upper scale; Figs. 12 and 13 to scale at left; Fig. 14 to lower scale.
Abbreviations: 1, first, or infradental, oral papilla, 2, second, or apparent, outer papilla. 3, third, or true, outer papilla, reflexed below second papilla. A, adoral plate. AM, ambu-lacral vertebra. D, upper arm-plate. G, genital cleft. GS, outer genital scale. L, lateral arm-plate. M, madreporite. N, naked adoral interradial region. O, oral shield. PL, orel plate, S, radial shield. SP, arm-spine. T, tooth. TE, tentacle-scale. V, lower arm-plate.
Colour: mottled fawn, brown, and grey; the largest oral papillae brown, the arms whitish below.
Type locality: Alert station 2, Pelorus Sound, 25 to 30 fathoms, shell detritus and mud, December 26, 1951; coll. W. H. Dawbin; three specimens.
Holotype: in the Zoology Museum, Victoria University College.
Ctenamphiura has, till now, been a monotypic genus known only from two specimens of C. maxima (Lyman, 1879) which were taken from 28 fathoms at Challenger station 188, western end of Torres Strait. No specimens had been reported since; accordingly, the finding of three specimens of the genus, representing an undescribed species of it, was a great surprise and a notable result of the Alert investigations.
In a preliminary announcement of the rediscovery of the genus (Fell, 1952a), it was stated, inter alia, that Ctenamphiura is characterized by its large outer oral papillae which exceed in size the inner papillae. On subsequent study, I found the true relations to be as stated above and as illustrated in Fig. 14—where the infradental papillae have been drawn overturned to show their real size and the peculiar reflexed condition of the true outer papillae indicated.
C. dawbini and the genotype, C. maxima, share in common not only the generic characters as defined by Verrill (1899)—that is, the characteristic structure and arrangement of the jaws and accessory plates and oral shields—but also the fact that the arm-spines are arranged to form combs. Since it is obvious that Verrill had these combs in mind when he erected the genus, it seems strange that he omitted to note their presence when defining it; the diagnosis clearly should include the character. The two species agree also in the large size of their tentacle scales and the lumpy character of the disc-plates. C. dawbini is distinguished from the congener by having only one (instead of two overlapping) tentacle-scale, and by the partly naked character of the underside; also by the reflexion of the spiniform oral papillae.
Ophiactis Luetken, 1856
Ophiactis resiliens Lyman, 1879
- Island Bay Shelf, ca. 10 fathoms, on rock from sea-bed tangled in fisherman's trawl, July, 1950; C. A. Fleming; two specimens.
Ophiactis profundi Ltk. & Mrtsn., 1899
- Island Bay Shelf. 10 fathoms (as above); five specimens.
Neither of the above species has spines on the disc; they are separable easily by the fact that the former is regularly five-armed, the latter six-armed, and transversely fissiparous, having usually three large and three small arms.
Ophiocentrus Ljungman, 1867
Ophiocentrus novae-zelandiae Gislen, 1926
- Lachlan station 617/50. In bottom-mud off survey-beacon anchor, November, 1950; 40° 15′·0 S., 174° 57′·5 E., ca. 50 fathoms; one specimen.
Ophioncreis Luetken, 1859
Ophionereis novae-zelandiae Mrtsn., 1936
- Alert station 19, one specimen.
- Island Bay Shelf, ca. 10 fathoms, July, 1950; one specimen.
The disc is grey, the arms grey with narrow black bands at I mm. intervals. The coloration is retained but little altered in spirit.
Ophionereis fasciata (Hutton, 1872)
- New Golden Hind station NGH L14, one specimen.
- Alert stations: 4. one specimen; 13, one specimen; 20, six specimens; 18, one specimen.
H. L. Clark (1928), after examining a good series of the Australian Ophionereis schayeri (M. & T., 1844), considers that the differences which Mortensen (1924) found between this and the New Zealand form "... are by no means as constant as could be desired ..." Clark had, however, only a few New Zealand specimens to go upon, and reached no conclusion.
I have examined over the past few years a very extensive series of New Zealand forms from widely scattered localities, including the Auckland Islands, and find that Mortensen's diagnosis of O. fasciata holds good. In one specimen from Alert station 18, however, although the skeletal characters are normal and the structure of the genital clefts and their relationship to the oral shield and general undersurface is as for O. fasciata, the coloration is unlike the usual marbled combination of black, grey, brown, and fawn mottling and banding; instead, there is a greyish-purple disc and arms, lighter below.
Ophiocoma L. Agassiz, 1835
Ophipcoma bollonsi Farquhar, 1908
- Alert station 13, two specimens.
- East coast of Otago, between Moeraki and Taiaroa, 40 fathoms; P. M. Ralph, November, 1951; four specimens.
- Off Banks Peninsula, 80 fathoms, 44° 15′·0 S., 173° 31′·0 E.; coll. G. A. Knox; arm fragments.
The specimens from the stations to the east of the South Island are large ones, the largest having R, 10 mm., r, 14 mm. The colour in all cases is dark brownish-purple. H. L. Clark has treated club-shaped spines in Ophiocoma as being of systematic value; however, the presence of three kinds of spines on otherwise similar material from off Banks Peninsula would confirm Mortensen's opinion that club-shaped spines are pathological.
Ophioptens E. A. Smith 1877
Ophiopteris antipodum E. A. Smith, 1877
- Off east Canterbury coast, 40 fathoms; P. M. Ralph; one specimen; see Fell (1951).
Pectinura Forbes, 1843
Pectinura maculata (Verrill, 1869)
- New Golden Hind station NGH 57a, one specimen.
- Alert stations: 3, one adult; 12, one young specimen; 13, eight young specimens and six half-grown.
- Ruapuke oyster beds, Foveaux Strait, 12 fathoms, February, 1951; B. M. Bary; two specimens (extremely abundant).
The young of this large species have not hitherto been recognized; indeed, their colouring and general appearance are so different from that of the adult that, were it not for the taking of a consecutive series of stages, they would not have been recognized on the present occasion. In the stage at which the animal is about two centimetres to four centimetres in diameter, the arms are vermilion and the disc ochre. with a dark orange periphery, orange below. In dissecting a specimen from station 13 (Dusky Sound), I was surprised to find the stomach packed with what appeared to be some kind of flower (the specimen was dredged in 12 to 15 fathoms). Subsequently, Dr. J. G. Gibbs, of Victoria University College Botany Department, identified the material as anthers of Southern Beech, Nothofagus sp. page 25 This was later confirmed by Mr. W. F. Harris, of the New Zealand Department of Scientific and Industrial Research; he states: 'The pollen was of Nothofagus; 52 grains were measured and pore counts were made simultaneously on 26 grains. There were 16 per cent. with seven pores and 84 per cent. with eight pores. The size range was 29μ to 39μ, with an average of 34μ." The ophiuroid had been selectively feeding upon the anthers, since nothing else was in the stomach. This is only the second record to my knowledge of an echinoderm feeding upon terrestrial plant material; the other is the case of a deep-sea echinoid in the East Indies which feeds upon the leaves of dicotyledonous trees washed out to sea by rivers.
Pectinura gracilis Mrtsn., 1924
- Alert stations: 2, two large specimens; 3, one specimen: 13, fifteen small individuals; 20, eight specimens; 25, one specimen.
- Island Bay Shelf, 10 fathoms, July, 1950; one specimen.
The species is evidently the South Island equivalent of P. cylindrica, as no specimens of the latter have ever been reported south of Cook Strait.
Ophiozonoida H. L. Clark 1915
Ophiozonoida picta H. L. Clark, 1915
- Five miles north of Cape Palliser, February, 1947, coralline bottom, 50 fathoms; F. Abernethy; one specimen.
- Ten miles south of Cape Campbell, May, 1947, 50 fathoms, coralline bottom; F. Abernethy; one specimen.
Ophiura Lamarck, 1816, emend. Matsumoto
Ophiura chathamensis sp. nov. (Figures 15 to 20)
Dimensions: minor radius, 3 mm.; arms broken, but probably three times minor radius.
Disc, circular, flattened. Aboral surface covered by imbricating, thin, closely adpressed scales of varying size; the larger ones occur at the centre, at the ambitus, in the interradii, and between the radial shields. Primary plates indistinct. Radial shields pearseed-shaped, distally contiguous, separated proximally by a wedge of six or eight polygonal plates, and extending less than half-way to the centre of the disc. Adoral surface completely sealed by closely imbricating uniform plates. Genital clefts extending from the oral shields to the upper part of the arm-base, with genital papillae forming the interradial border. Oral shield large, broadly pentagonal, with a convex distal base, concave sides, and an obtuse proximal angle. Adoral plates small, broader than long, meeting broadly within, contiguous only with the proximal border of the oral shield. Oral plates larger than the adoral plates, with three pairs of oral papillae.page 26
Ophiura chathamensis sp. nov.
Fig. 15.—Aboral view. Fig. 16.—Lateral view of arm-segment Fig. 17.—Adoral view.
Figs, 18 to 20.—Aboral, adoral, lateral views respectively of young individual of Ophiura sp., doubtfully referred O. chathamensis. All to scale shown.
Abbreviations:. A, adoral plate. AC, basal arm-comb. D, upper arm-plate. 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 pore, with scales. V, lower arm-plate.
Arms: provided with basal arm-combs, each carrying about ten papillae. Upper arm-plates contiguous on the proximal four segments, thereafter isolated, their shape changing from subquadrate at the base to longitudinally ovate at the fourth plate and beyond, the narrow end of the ovate plates being proximal. Lateral plates meeting both above and below, save on the segments bearing the first four upper arm-plates, where the lateral plates meet below only. They bear three slender, pointed arm-spines, of which the uppermost is longest, equal in length to one segment, the lowermost smallest. Lower arm-plates small, not contiguous, mostly fan-shaped with a proximal obtuse angle and convex distal border; but those of the second and third arm-segments are transversely rhomboid, and that of the first segment longer than broad. Second oral tentacle-pores large, opening into the oral clefts, each ringed by nine or ten small scales. The first three or four lateral plates of the arm carry each a tentacle-pore, the first one large with four or five scales, the second of medium size with three scales, the third (and fourth, if present) minute with one or no scale; beyond, there are no pores.
Colour, in spirit, white.
Type locality: Discovery station 2733, Chatham Rise, west of Chatham Islands, 30 metres, November 4, 1950; one specimen.
Holotype: Zoology Museum, Victoria University College.
From Ophiura rugosa, the only other species of Ophiura known from New Zealand, O. chathamensis is sharply distinguished. The former has large, rounded aboral plates arranged in a symmetrical pattern, the proximal under arm-plates are contiguous, and the arm-spines are very short. O. chathamensis shares with Ophiocten hastatum, a generic relative, the character of having slender spines in groups of three, the uppermost elongate; but it is distinguished by lacking the uniformly fine scaling of the aboral surface and by the larger and differently shaped radial shields. Benham's Ophiura kermadecensis is now referred to Amphio-phiura, and is not similar to the present species.
Of the Pacific species of Ophiura, O. chathamensis appears to be more nearly related to Ophiura ooplax (H. L. Clark) than to any other—a species which ranges from Japan to South Australia. The resemblance is most marked in the form of the radial shield, the general structure of the arms, and the three slender arm-spines. The differences, however, are considerable: the arm-combs are lost in the adult O. ooplax, where, also, all the arm-spines are elongate. In O. chathamensis, there are three oral papillae (eight or nine in O. ooplax), and the tentacle-pores decrease in size more rapidly than they do in the latter species. O. Chathamensis also has a finer aboral scaling than O. ooplax.
The ophiuroid illustrated (Figs, 18 to 20) was taken with this species at Discovery station 2733. Despite the large oral shields, which suggest Amphiophiura, it is clearly an Ophiura, as the rapid declension of the tentacle-pores indicates. Although the aboral surface of the disc is markedly different, and there are only page 28 two arm-spines, it exhibits considerable resemblance to O. chathamensis, of which it might be a juvenile stage. I therefore refrain from doing more than illustrate its structure.
Ophiomisidium Koehler, 1914
Ophiomisidium irene sp. nov. (Figures 21 and. 22)
Dimensions: R, 4·0 mm.; r, 1·5 mm.; ratio R/r, 2·7. The holotype and syntypes are all similar.
Disc: pentagonal, flattened above and below. The aboral surface of the disc is made up of a symmetrical mosaic of 26 plates, all polygonal and interlocking. These comprise the following; At the centre lies the pentagonal dorso-central: it is surrounded by a ring of live hexagonal primary radials; outside these is a ring of fifteen plates, five of them pentagonal primary interradials. the remainder the five pairs of radial shields. The latter are pentagonal and contiguous. A transversely elongate secondary interradial intervenes between adjoining pairs of radial shields. The adoral surface is largely made up of the first lateral arm-plates. The oral shield is vestigial, rhomboid. Adoral plates are longer than broad, contiguous over most of their length, meeting the oral shield only on their distal borders, their lateral borders emarginated by the first large tentacle-pore (whose scale they carry). The oral plates are broader than long, broadly contiguous with each other as Well as with the adoral plates. Oral papillae represented only by a narrow marginal bar along each oral plate.
Anms: short, expanded at the base, tapering distally to a slender extremity, nine arm-segments. There are five upper arm-plates; the first fan-shaped, contiguous with the radial shields, and overlapping upon the second; the third, fourth, and fifth also fan-shaped, but not contiguous, and diminishing in size rapidly in that order. Distal arm-segments without upper arm-plates. Lateral arm-plates well developed on all segments, the first far the largest, the second much smaller, the third and succeeding ones tapering more gradually. The first lateral arm-plates of each side are broadly contiguous not only with each other, but also with their corresponding member of the adjoining arm. Hence they form a closed ring completely investing the oral skeleton. They comprise most of the interradial area below, all but obliterate the oral shields, and completely obliterate the genital clefts. The lateral plates meet above and below on all segments except the first, where they meet below only. The first and second lateral plates bear on their free edges two flattened scales, which evidently represent modified spines; the scales form a fringe round the whole disc. The third and fourth lateral plates carry each only one short, stumpy spine, and thereafter there are no more spines. There are five lower arm-plates, the innermost largest, the second and third moderately large, the outer two minute. The first three lower arm-plates are more or less pentagonal, having their lateral borders emarginated by the three large tentaclepores.page 29
Ophiomisidium irene sp. nov.
Fig. 21.—Aboral view. Fig. 22.—Adoral view.
Abbreviations: A, adoral plate. D, upper arm-plates. DC, dorso-central primary plate of disc. I, primary interradial plate of disc. II, secondary interradial plate of disc. L, lateral arm-plates. LA, spines of basal lateral arm-plate, modified as flattened scales. O, oral shield. PL, oral plate. R, primary radial plate of disc. S, radial shield. V, lower arm-plate.
Colour, in spirit, white; the outer parts of the aboral primary plates are porcellanous, their inner parts translucent.
Type locality: Discovery station 2733, Chatham Rise, 30 metres, November 4, 1950; sixteen individuals.
Holotype: Zoology Museum, Victoria University College.
Koehler (1914) founded Ophiomisidium to accommodate three species specially characterized by the entry of the arm-plates into the formation of the oral surface of the disc. The first lateral arm-plate makes up most of the interradius, the first lower arm-plate is large, and is succeeded by two others not quite so large.
Of the three species included, O. pulchellum (Lyman, 1878) and O. speciosum Koehler (1914) have the first lateral arm-plates less enlarged, so that the genital clefts are still present. O. flabellum (Lyman, 1878), known from the continental shelf off New South Wales, has the first lateral arm-plate so large as to obliterate the genital clefts, and the oral shields are rudimentary. Ophiomisidium irene therefore belongs to the O. flabellum type in this regard. It is distinguished from the latter species in many respects, notably the more attenuated distal arm region, the larger upper arm-plates, the more compact form of the primary interradial plates, and by the fact that the spines of the first two lateral plates are modified into large rounded scales.
The delicate porcellanous and translucent lustre of the plates and the symmetry of the whole animal combine to make this tiny sea-star a microscopic object of great beauty. Although no species of Ophiomisidium has hitherto been taken in New Zealand waters, representatives are probably very common, since no fewer than sixteen specimens were taken in the single Discovery haul at station 2733.
Ophiomastus Lyman, 1878
Ophiomastus stellamaris sp. nov. (Figures 23 to 27)
Dimensions: R, 10·0 mm.; r, 1·5 mm.; ratio R/r, 6·7. The arms are relatively shorter in immature forms.
Ophiomastus stellamaris sp. nov.
Fig. 23.—Aboral view. Fig. 24.—Lateral view of disc and base of arm, seen from radial aspect, to show its hemispherical tumidity. Fig. 25.—Adoral view. Figs. 26 and 27.—Aboral and oblique lateral views of young individual, showing large primary plates.
Figs. 23 to 25 to scale shown below. Figs. 26 and 27 to scale at right.
Abbreviations: A, adoral plate. D, upper arm-plate. DC, primary dorso-central plate of disc. I, primary interradial plate of disc. L, lateral arm-plate. O, oral shield. OP, oral papillae. R, primary radial plate of disc. S, radial shield. SP, spine of lateral arm-plate. TE, tentacle-scale. V, lower arm-plate.
Arms: Upper arm-plates fan-shaped, as long as broad, with a convex distal border, contiguous only in the proximal part of the arms, smaller distally. Lateral arm-plates meeting above and below, except on the basal segments, bearing each a solitary arm-spine on the distal, median border of the lower side. The arm-spine is small but robust, conical, directed distally, not visible from above. The lower arm-plates are contiguous and longer than broad on the proximal two or three segments; beyond, they are not contiguous, but become smaller, and relatively broader than long; they have a prominent convex distal border, and the proximal half of each lateral border is emarginated by the large tentacle-pore. There is a single, large, circular, flattened tentacle-scale, attached to the lateral plate, completely covering the pore.
Colour, in spirit, creamy white.
Type locality; Discovery station 2733. Chatham Rise, 30 metres, November 4, 1950; eleven specimens.
Holotype: Zoology Museum. Victoria University College.
Remarks.—With Ophiomastus tegulitius Lyman, the only species of the genus hitherto known from New Zealand (Cook Strait. 275 fathoms, H.M.S. Challenger), the present species shows no close relationship. The slit-like tentacle-pores, the two tentacle-scales (small and semi-lunar in shape), the paired laterally-borne arm-spines, and the more rapidly tapering arms are some of the distinguishing features of the former. On the other hand, O. stellamaris does show a close resemblance to Ophiomastus secundus Lyman, a species known only from West Indian and central Atlantic seas. The latter species shares with the present one the possession of a single large tentacle-scale, and may have only one arm-spine. However, in O. secundus, two arm-spines occur, even in small individuals, and they are carried, furthermore, on the sides of the arm, not below; also, the oral plates do not carry oral papillae, only a marginal border representing them. In most other respects, the two species are quite similar. From O. perplexus Koehler and O. tumidus Koehler, the species likewise differs in having only one arm-spine.