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Volume 14, 1881
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Art. XXIV.—Additions to the New Zealand Crustacea.

[Read before the Philosophical Institute of Canterbury, 13th October, 1881.]

Plate VIII.

This paper contains the descriptions of three new species of Crustacea, two belonging to the Brachyura and one to the Isopoda. I also describe the male of a species of Amphipoda, the female only having been hitherto known.

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Brachyura.

Genus Hymenicus, Dana.
(Miers' Cat. N.Z. Crustacea, p. 50.)

Hymenicus marmoratus, sp. nov. Plate VIII., fig. 1.

Garapace smooth, naked and flat; sub-triangular with the sides arched, about as broad as long; front projecting and trilobate. Antero-lateral margin with two teeth, the posterior one sharp, long, and very distinct, the anterior one short and blunt. Abdomen of male sub-triangular, first segment broadest and more or less rectangular, penultimate segment narrower than the preceding, the last segment sub-triangular, rounded at the apex. Anterior legs rather large and swollen; tarsi of the remaining legs somewhat densely haired, the other joints being sparsely haired. Colour-variously marked with white and reddish-brown. Length .25in.

Hab. Common amongst sea-weed in rock-pools in Lyttelton Harbour.

Though common at Lyttelton Harbour this crab does not appear to have been hitherto described. It is closely allied to Hymenicus varius, but differs in the shape of the carapace, in having the two teeth on the anterolateral margin well marked, and also in colour.

Genus Elamena, M.—Edwards.
(Miers' Cat. N.Z. Crustacea, page 52).

Elamena (?) lacustris, sp. nov.

Carapace nearly circular, rather broader than long. Rostrum broad, strongly depressed, concave above, sides parallel, obtusely pointed at the end. Antero-lateral margin of the carapace with two nearly obsolete teeth. Last pair of legs much shorter than the preceding. Colour (in spirit)- carapace brown, legs yellowish, spotted with brown. Breadth .15in.

Hab. Lake Pupuke (fresh water), North Shore, Auckland.

This species is remarkable from the fact that it is an inhabitant of fresh water.

I am somewhat doubtful about referring it to Elamena, as I have only seen a single specimen, a female.

Professor Hutton kindly handed over this and the preceding species to me for description.

Types of both have been lodged in the Canterbury Museum.

Isopoda.

Genus Anthura, Leach.
(Bate's and Westwood's Brit. Sessile-eyed Crust., vol. ii., p. 157.)

Anthura, (?) flagellata, sp. nov. Plate VIII., fig. 2.

Body long, slender, sub-cylindrical, thoracic segments sub-equal. Antennæ near equal, the inner one with a distinct flagellum. First three pairs of thoracic legs sub-chelate, the first pair being considerably larger than the

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New Zealand Crustacea.

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two following, and having the hand stout and ovate, and the finger long and curved; the second and third pairs similar in shape and equal in size; the four posterior pairs are all nearly equal to one another, and are nonchelate. First five abdominal segments confluent; the last segment has its posterior edge notched at the centre. Its appendages are broad, operculiform, and biramous, the inner branch formed of a single joint, broad and concave, enclosing the other branch, which has two broad joints, the basal one being much longer than the terminal joint. The terminal segment (telson) squamiform, rectangular, with the posterior angles rounded. The posterior edges of the telson and of the appendages of the last abdominal segment are fringed with numerous long setæ. Length, .3 in.

Hab. Among seaweed in rock-pools, Lyttelton Harbour.

This species differs from Anthura in that the first five (instead of four) abdominal segments are confluent and that the inner antenna has a distinct, flagellum, but as I have only a single specimen I have not made a new genus for it.

Amphipoda

Microdentopus maculatus, G. M. Thomson (Ann. & Mag. N.H., ser. v., vol. iv., p. 331).

This species was described by Mr. Thomson, from a single specimen, a female. It appears to be moderately common amongst seaweed in the rock-pools at Lyttelton. Amongst some specimens answering very well to his description I took one which also agreed with that description in every particular except as regards the gnathopoda. These (plate VIII., fig. 3) are very peculiar, the meros is produced inferiorly into a long acute spine reaching slightly beyond the extremity of the succeeding joint, the carpus; this spine bears a small tuft of setæ about one-third of its length from its extremity. The carpus is large, and is rather more than twice as long as broad. The propodos is much smaller; its inner edge is fringed with numerous setæ. The last joint forms a strong finger slightly curved at the end, its inner edge is smooth; numerous long setæ arise at its base. The second pair of gnathopoda are of more normal shape, the meros not being produced into a spine.

The first pair of gnathopoda closely resemble those of Aora gracilis and Aora typica,* though slightly different from both of them. Mr. Thomson has taken Aora typica in Dunedin Harbour, and he speaks of its resemblance to Microdentopus maculatus, and hints that they may possibly be male and female of the same species. The animal I have, though distinct

[Footnote] * “Brit. Mus. Cat. Amphip. Crust.,” pp. 160–2, pl. xxix., figs. 7 and 8.

[Footnote] † “Trans. N.Z. Inst.,” vol. xiii., p. 218.

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from Aora typica, is, however, so very like Microdentopus maculatus in every part except the gnathopoda that I have little doubt that it, and not Aora typica, is really the male. This is also confirmed by the fact that the two were found together.

Description Of Plate VIII.
Fig. 1.

Hymenicus marmoratus.

a.

Third (external) maxillipede × 22.

b.

Second maxillipede × 22.

c.

Abdomen of male × 5.

Fig. 2.

Anthura (?) flagellata.

a.

Antennæ × 22.

b.

Third thoracic leg × 22.

c.

Sixth thoracic leg × 22.

d.

Abdomen and telson × 22.

Fig. 3.

Microdentopus maculatus.

a.

First gnathopod of male × 22.

b.

Second gnathopod of male × 22.