Diagnosis : Tentacles 15, large, non-retractile. Ventrolateral pedicels large, in a single row throughout each radius. Midventral radius naked. Dorsal radii each with a crowded series of very numerous retractile slender processes, usually in a double row.

Type Specimen: Ilyodaemon maculatus Theel.

Remarks: The genus is widespread in the Indo-west-Pacific (I. fimbriatus, I. maculatus and I. abstrusus) and off Japan (I. ijimai and I. muriense) in depths ranging between about 159 metres and 1,000 metres. The fact that Ilyodaemon is now known to occur in New Zealand waters considerably extends the known range of distribution, and it seems likely that the genus will be found to have a far wider distribution than formerly has been supposed.

Ilyodaemon embraces five species, which may be distinguished as follows:

Ilyodaemon abstrusus Sluiter Text-fig. 5, figs. 1–4

Ilyodaemon abstrusus Sluiter, 1901a, p. 24; 1901b, p. 69, Pl. IV, figs. 1–3, Pl. IX, fig. 9.

Material Examined: Marine Dept. Stn. 23, 1 specimen; Stn. 31, 4 specimens.

Description: Total length ranges from 108mm to 142mm. Body elongate, approximately four times as long as broad. Bodywall extremely slimy, thick, gelatinous. Midventral radius naked, lateral ventral radii each with a single row of soft triangular processes, of average length 10mm. Processes regularly spaced along radii, numbers varying between 16 and 20 in each radius, although 18 processes is usual number. Lateral dorsal radii each carry approximately 55 pairs of short (5mm long) processes, regularly arranged; thus there are two rows of processes in each dorsal radius. Mouth ventrally turned, anus terminal.

In five specimens tentacle numbers are 11, 10, 15, 14, 14. Anterior end of each specimen damaged, normal tentacle number indeterminate, although there are probably more than 15.

Colour in alcohol dark purple overall, dorsal processes violet, ventrolateral processes lighter in colour. Tentacles dark brown, with leathery circular terminal discs. Intestine purplish-black, describing a large S-shaped loop. Polian vesicle large, bulbous. Gonad consists of small deep purple tufts of caeca.

Calcareous deposits include large wheels, smaller wheel-shaped perforated deposits, spinous rods. Large wheels (Text-fig. 5, fig. 2) regular, with 9–11 spokes and some central perforations. Wheels with 9 spokes (45%), or with 10 (40%), most commonly present. Diameter of wheels ranges from 0.085mm to 0.13mm; page 21

Text-fig. 5.—Ilyodaemon abstrusus Sluiter: Fig. 1, rods from dorsal processes; Fig. 2, large wheels; Fig. 3, rods from tentacles; Fig. 4, small wheels. ?Laetmogone violacea juv.: Fig. 5, rods from ventral pedicels; Fig. 6, small wheel; Fig. 7, large wheels.

page 22 average diameter 0.1mm. Small wheels (Text-fig. 5, fig. 4) of average diameter 0.04mm typically have four larger central perforations and twelve spokes. Margin of small wheels often slightly indented opposite each spoke. In dorsal bodywall, large and small wheels present, sparsely scattered. Ventrally, both types present, more closely aggregated.

Dorsal processes contain only small wheels in large numbers scattered irregularly. Ventral processes contain large wheels near bases; toward the distal extremities these are replaced by numerous rods of varying shape (Text-fig. 5, fig. 1) up to 0.5mm in length. Some rods bear a few small spines. In stems and discs of tentacles are curved rods (Text-fig. 5, fig. 3) up to 0.6mm long, with weakly spinous ends.

Remarks : These specimens are representatives of Ilyodaemon abstrusus, a species first described by Sluiter (1901a). Sluiter's largest specimen was 170mm in length, and the number of pairs of dorsal processes was given as 70 to 80. It is possible that this number increases with growth. However, none of the present specimens have less than 50 pairs of dorsal processes. The tentacles in Sluiter's specimens are violet, while here they are brown. In spite of such differences, it is apparent that the New Zealand specimens represent Sluiter's species.

In the specimen from Marine Dept. Stn. 31, five nematodes were found in the coelomic cavity, near the posterior end of the intestine. They were free and unattached, lying entwined in the small muscle fibres supporting that part of the intestine. Total length of these worms ranges from 16m to 30mm. The colour in alcohol approximates that of the intestine, although two of the specimens are light brown. These specimens are as yet unidentified. This is possibly the first record of the presence of nematodes in an elasipod holothurian.

The relationship between the "host" and its "parasites" is not clear. The intestine of the specimen contained no other nematodes, nor was there any evidence of damage to surrounding tissues in the region in which the nematodes were found. As there are no respiratory trees, it is difficult to imagine how the nematodes came to enter the coelomic cavity, unless they penetrated the wall of the intestine, or somehow entered the water-vascular system.

Diagnosis: Tentacles 20, large, non-retractile. Ventrolateral radii with large pedicels in a single row throughout each radius. Midventral radius with a double row of pedicels. Dorsal surface with a crowded series of very numerous slender processes along each side. Deposits large wheels and small wheel-shaped plates.

Type Species: Pannychia moseleyi Theel.

Remarks: A genus containing five species, of which the type species is wide ranging in the Pacific Ocean in depths of 500–2.000 metres.

Pannychia moseleyi Theel

Pannychia moseleyi Theel, 1882, p. 88, Pls. XVII, XXXII, figs. 1–13; Ludwig, 1894, p. 95; Sluiter, 1901b, p. 71; Mitsukuri, 1912, p. 207; Ohshima, 1915, p. 235; Djakonov, Baranova and Saveljeva, 1958, p. 360.

Material Examined: None.

Remarks: Theel (1882) described two specimens of this species, one taken from east of Australia (34° 8′ S., 152° 0′ E.) in 1,719 metres, the other from off New Zealand (37° 34′ S., 179° 22′ E.) in 1,260 metres. Since that time the species has been recorded from several localities in the Pacific Ocean (see Ohshima, 1915, p. 235).

Diagnosis: Tentacles 15, large, non-retractile, ventrolateral radii with large pedicels in a single row throughout each radius. Midventral radius naked. Dorsal page 23 radii each with a single series of extremely elongated, flexible, slender, non-retractile processes. Deposits include wheels and often cruciform bodies.

Type Species: Laetmogone wyvillethomsoni Theel.

Remarks: This genus contains about ten species, of which two, L. violacea Theel and L. wyvillethomsoni Theel, are known to be cosmopolitan. Deichmann (1930) has indicated that these two species have undoubtedly been confused on many occasions, because of their great similarity to each other. Species of Laetmogone have been taken in depths ranging from 200 metres to 3,500 metres.

Laetmogone violacea Theel Text-fig. 6

Laetmogone violacea Theel, 1879, p. 11; Theel, 1882, p. 78, Pl. 13, figs. 1–3, Pl. 36, figs. 20–24, Pl. 42, fig. 2; Perrier, 1902, p. 390, Pl. 19, figs. 1–7; Augustin, 1908, p. 21; Mitsukuri, 1912, p. 192, Pl. 6, figs. 52–54, Text-fig. 36; Ohshima, 1915, p. 237; Greig, 1921, p. 9; Herouard, 1923, p. 37; Mortensen, 1927, p. 361, figs. 213–4; Deichmann, 1930, p. 120; Heding, 1942, p. 14, Text-fig. 14.

Cryodora spongiosa Theel, 1879, p. 9.

Laetmogone spongiosa Theel, 1882, p. 80, Pl. 14, figs. 1–3, Pl. 39, figs. 5–6.

Laetmogone jourdaini Petit, 1885, p. 9.

Laetmogone brogniarti Perrier, 1886, fig. 241.

Material Examined: N.Z.O.I. Stn. C.619, 3 specimens. Marine Dept. Stn. 11, 6 specimens; Stn. 23, 1 specimen; Stn. 27, 3 specimens. Dominion Museum, B.S.209, 1 specimen.

Description: Body elongate, flattened ventrally, about three times as long as broad. Mouth subventral, anus subdorsal. Total length ranges from 57mm (an autoeviscerated specimen) to 102mm. Tentacles 15 (14 in one specimen). Dorsal surface with elongate processes in each radius (Text-fig. 6, fig. 1), ventrolateral radii with short, broad pedicels (Text-fig. 6, fig. 5), midventral radius naked. Colour in alcohol light grey with a purple tinge; dorsal processes dark reddish-purple. Bodywall thick, soft, gelatinous. Tentacles with grey stems and a brown leathery terminal disc.

Dorsal processes up to 25mm long, while ventral pedicels are up to 13mm long. Variation in the number of processes and pedicels is shown in following table:

Average number of dorsal processes 24; ventral pedicels 14.

Fragile calcareous ring a continuous network of calcareous material; radial areas with faint anterior processes for attachment of radial muscles. A thinwalled intestine describes a very large loop (Text-fig. 6, fig. 1) ; cloaca attached to bodywall by some fine muscle fibres. Intestine transparent; cloaca light violet, opaque. Single Polian vesicle elongate, cylindrical (Text-fig. 6, fig. 1), arising from ring vessel in left ventral interradius. Stone canal runs posteriorly for short distance in dorsal mesentery, terminating in a minute nodular madreporite, which opens to exterior near opening of genital duct.

Text-fig. 6.—Laetmogone violacea Theel: Fig. 1, internal anatomy, margins intact, dorsal view; Fig. 2, anchor shaped spicule of doubtful origin; Fig. 3, spinous deposits from ventral bodywall; Fig. 4, deposits from dorsal processes; Fig. 5, entire animal, ventral view; Fig. 6, portion of gonad; Fig. 7, tentacle deposits; Fig. 8, wheels (a, b, developing; c, small; d, large); Fig. 9, "endplate" deposits from ventrolateral pedicel; Fig. 10, rods from ventrolateral pedicels. Abbreviations: an., anus; clo., cloaca; c.r., calcareous ring; desc. int., descending intestine; dors. proc., dorsal process; g.d., genital duct; gon., gonad; g.pap., genital papilla; g.tub., genital tubule (caecum); mo., mouth; oes., oesophagus; ped., pedicel; p.v., polian vesicle; r.l.m., radial longitudinal muscle; ten., tentacle; v.l.m., ventral longitudinal muscle.

Gonad a large bunch of dichotomously branching genital caeca (Text-fig. 6, fig. 6). Genital duct short, opening to exterior at tip of genital papilla, a short distance from anterior end of body in mid-dorsal interradius. Longitudinal muscles five broad undivided dark brown straps.

Calcareous deposits include wheels, spinous spicules. Wheels of two types, large and small. Large wheels (Text-fig. 6, fig. 8d) typically have 8–9 spokes and average 0.9mm in diameter. Smaller wheels (Text-fig. 6, fig. 8c) have 12–13 spokes, and are 0.05mm in diameter. All wheels approximately saucer-shaped, lying with concave surface facing outwards. Stages in development of large wheels commonly found (Text-fig. 6, fig. 8 a, b). Three- to six-armed spinous deposits of average length 0.1mm are numerous in ventral bodywall, but rare dorsally (Text-fig. 6, fig. 3).

Dorsal processes contain wheels, together with numerous rods and three-armed deposits, often with weakly spinous extremities (Text-fig. 6, fig. 4). Small wheels more common near distal extremities of processes, while large wheels mostly found near bases. In ventrolateral pedicels wheels numerous, and at distal extremity of each pedicel is an "endplate" composed of an aggregation of small, smooth deposits of variable shape (Text-fig. 6, fig. 9), surrounded by a ring of curved spinous rods (Text-fig. 6, fig. 10).

Tentacles contain wheels, as well as spinous rods of variable size (Text-fig. 6, fig. 7). Average length of rods 0.4mm. In walls of genital caeca are small spinous rods of average length 0.2mm.

In dorsal bodywall, a spicule of unusual character, resembling an anchor, was found (Text-fig. 6, fig. 2). This spicule is 0.2mm in length, and is possibly not of holothurian origin.

Remarks: The variation shown by the dorsal processes and ventrolateral pedicels is quite considerable. The spiculation can also vary greatly. Heding (1942) described variation in specimens collected during the "Ingolf" Expedition, and considered that such differences are too slight to be used for distinguishing the numerous forms of this species.

This is the first record of L. violacea from New Zealand. Its occurrence here is not unexpected, as L. violacea is one of the most widespread of elasipod species, being known from the Arctic, Atlantic and Pacific Oceans. Heding (1942) notes that "L. violacea appears to be a cosmopolitic species, originating from the Indo-Pacific ..." The species is usually confined to deeper waters beyond the continental shelf, and has been taken from depths exceeding 1,800 metres.

?Laetmogone violacea Theel juv. Text-fig. 5, figs. 5, 6, 7

Material Examined: Marine Dept. Stn. 32, 1 specimen.

Description: The juvenile elasipod of total length 15mm has calcareous deposits greatly resembling those of Laetmogone violacea. Body contracted, skin thick, gelatinous, translucent, light purple. Lateral ventral pedicels and dorsal processes present, midventral radius naked.

Ventral processes elongate tubefeet, each about 4mm in length; a concave perforated endplate (0.5mm diameter) present, surrounded by curved spinous rods up to 0.5mm in length (Text-fig. 5, fig. 5) and small wheels (Text-fig. 5, fig. 6). Stems packed with spinous rods, which lie tranverse to longitudinal axes of tubefeet. There are 18 processes in left ventral radius, and 11 in right (damaged).

Dorsal processes deep red in colour, up to 6mm in length, with thick gelatinous bases. Processes less numerous than ventral tubefeet, there being only eight in left dorsal radius and nine in right. Calcareous deposits in processes include numerous large and small wheels (Text-fig. 5, figs. 6, 7).

Deposits apparently lacking from ventral side, but wheels common dorsally. Smaller wheels are of average diameter of 0.037mm, with 12 spokes and four page 26 central holes. Large wheels are of average diameter 0.146mm, typically with nine spokes, although wheels with more or less than nine spokes not uncommon; raised central boss has about six perforations.

Remarks : There is little doubt that this is a juvenile of an elasipod, of the genus Laetmogone, or a closely allied genus. However, there are some puzzling features about the specimen. The ventral processes are more numerous than the dorsal processes. This is not the case in L. violacea, although it is quite possible that L. violacea does not achieve its full complement of dorsal processes until later in its life history. Moreover, the ventral pedicels of the juvenile specimen exceed in number those of the adult. However, until new material becomes available it seems appropriate to consider this specimen a juvenile of L. violacea.

Diagnosis: Tentacles 15. Body elongate, flattened ventrally, arched dorsally. Midventral radius naked. Lateroventral radii each with approximately 50 narrow, elongate pedicels arranged in a single, often apparently double series. Dorsal radii each with about ten small retractile processes, regularly spaced. Deposits include wheels, circular perforated plates and spinous rods. Wheels and plates tend to be aggregated into scattered heaps on the dorsal side of the body.

Type Species: Bathygone papillatum Pawson.

Remarks: This genus differs from the others in Family Laetmogonidae in possessing peculiar heaps of calcareous deposits in the dorsal side of the body. Also the extremely numerous circular plates, while not unique to this family, are usually found in the papillae or pedicels, and are rare elsewhere.

Bathygone seems most closely related to Laetmogone Theel, differing from that genus in the smaller size of the dorsal papillae, and in the absence of accessory rods and cross-shaped deposits. Bathygone differs from Benthogone Koehler in having smaller ventrolateral processes, and more than one type of deposit in the bodywall.

Bathygone papillatum Pawson

Bathygone papillatum Pawson, 1965b, p. 77, figs. 7–11.

Material Examined: Marine Dept. Stn. 20, 7 specimens.

Remarks: This species has already been discussed elsewhere (Pawson, 1965b).

Diagnosis: Mouth ventral, surrounded by 15–20 tentacles. Body flattened or almost cylindrical. Ventrolateral radii each with a single row of ca. 15 retractile pedicels; midventral radius naked. Dorsal radii with numerous small processes in a single, sometimes double row. Deposits strongly vaulted wheels of one type, with an average diameter of 0.078mm.

Type Species: Benthogone rosea Koehler.

Remarks: This genus is monotypic, differing from other genera in the family Laetmogonidae in possessing wheels of only one type; these are not associated with any other deposits, except in the pedicels. Accessory deposits are spinous rods, which are found in the pedicels, processes and tentacles.

Benthogone rosea Koehler

Benthogone rosea Koehler, 1896, p. 114; Pawson, 1965a, p. 219, Pl. V, figs. 2–5 (synonymy).

Material Examined: "Tui" Stn. 098–17, 2 specimens.

Remarks: This species is described and discussed elsewhere (Pawson, 1965a).

Distribution: Off south-west Ireland, 1,200–1,765 metres, Bay of Biscay, off Azores Is., African coast to Cape Verde Islands, 1,000–2,320 metres (Mortensen, 1927). The occurrence of species north of New Zealand is unexpected, but it now seems likely that B. rosea is widespread in the Atlantic and southern Pacific Oceans.