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:

Dorsal Processes		Ventral Pedicels
Left dorsal radius	Right dorsal radius	Left ventral radius	Right ventral radius
28	27	15	14
ca. 23	ca. 19	14	12 (damaged)
ca. 26	ca. 23	16	16 (damaged)
—	—	15	—
24	23	15	15
—	—	13	15 (damaged)
23	22	14	15
24	21	13	15
25	23	14	13
24	24	13	13
—	—	14	13 (damaged)
—	—	13	— (damaged)
24	25	13	11
26	23	15	15

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.

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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.