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Some Amphipoda, Isopoda and Tanaidacea from Cook Strait

Group Ianirini

Group Ianirini

Iathrippa longicauda (Chilton), 1884. (Figs. 92107).

Janira longicauda Chilton, 1884: 250, pl. 18, fig. 2a.

Thomson, 1889: 265–266.

Tattersall, 1921: 200, pl. 1, fig. 6.

Ianira (Iathrippa) longicauda, Nordenstam, 1933: 173–176, text-figs. 40 a–h.

Iathrippa longicauda Nierstrasz, 1941: 286.

Diagnosis (Female) : Anterolateral angles of cephalon more or less rounded, not significantly produced anteriorly; rostrum triangulate, reaching distal end of 3rd peduncle segment of antenna 2. Epimeral plates visible dorsally, between lateral angles of segments 2–4 of body, posterodistally on segments 5–7, Pleotelson margins smooth, setose, slight page 18 indication distally of rounded median lobe. Uropods longer than pleotelson, rami somewhat lanceolate, inner the longer.

Body. Somewhat flattened, white in preserved specimen. Lateral margins of body setose.

Antennae. First: Reaches ½ along 5th peduncle segment of antenna 2; distal flagellar segments have each a flaccid sensory seta; flagellum of 15 segments, segments not especially widened. Second: 1st 4 peduncle segments together a little shorter than 5th, have several strong spines and setae; 5th ¾ length 6th; 5th and 6th have 1–2 long spines on each margin, setae; 1st flagellar segment nearly ½ length last peduncle segment; flagellum of 55 or more segments; accessory scale on 3rd peduncle segment, reaches end of 4th, has 4 end spines, setae.

Mouth parts. Maxilliped: Has 3 coupling spines; endite distal margin has 8–9 plumose setae; 7 large bush-setae, small spine on inner distal angle, longer one on rounded outer angle. Palp, 1st 3 segments as wide as endite, inner distal angles setose, 4th and 5th segments slender, distally setose, 5th 1/3 length 4th; 4th as long as 2nd and 3rd combined. Maxilla 1: Inner plate has 4 strong setae, fine bristles; outer has 11 denticulate spines. Maxilla 2: Outer plate lappets have 4 end setae each; inner has numerous end setae. Mandibles: Lacinia present; spine row of 9 denticulate spines; mandibular process long, not narrowing but truncate, has upper angle produced a little in tooth, lower has slender spine and 5–6 plumose setae; a few minute teeth on surface. Palp of 3 segments, 1st and 3rd subequal, about 2/3 length 2nd: 1st has about 3 setae on distal angle; 2nd has about 7 strong denticulate spines, comb-scales on surface; 3rd has long terminal spine, row of about 20 denticulate spines on concave margin.

Peraeopods. First: Carpus and propod subequal, carpus broader but not noticeably ovate, width not 1/3 length; posterior margin has 11–12 spines, seta or two, otherwise entire; propod posterior margin has 7–8 spines, otherwise entire. Dactylos has 2 claws, setae. Seventh: Carpus barely shorter than propod. has about 3 spines, setae, anteriorly; propod has about 5 spines; dactylos as in 1st. Others: All dactyli have 2 claws.

Pleopods. Third has exopodite slightly longer than endopodite, of 2 segments; endopodite has 2 plumose setae distally on inner margin, one on outer.

Operculum. Ovate, distally rounded, margins have short fine setae.

Uropods. Outer ramus about 2/3 length inner; peduncle ½ inner, widening distally; peduncle and rami all strongly spined and setose.

Material Examined: Station GUL (VUZ. 54), 1 female, 8.5 mm (Slides Oc. 4).

Distribution: Cook Strait; Lyttelton Harbour (Chilton); "Terra Nova" Station 96, 7 miles E. of North Cape, 70 fathoms, bottom fauna, 1 ovigerous female, 4 5 mm (Tattersall, 1921); Campbell Islands, Falkland Islands, S. Georgia, Magellan Straits, W. Chile (cf. Nordenstam, 1933).

Discussion : This specimen agrees quite well with Chilton's original description, and with Nordenstam's supplementary details. Tattersall's figure is a little generalised and even inaccurate since he shows the epimeral plates as part of the lateral margins of the segments. It should be noted, however, that the dactyli in this specimen all have 2 claws whereas Nordenstam mentions 3.

I have followed Nierstrasz rather than Nordenstam in generic classification, not because of any strong views on the subject but because Nierstrasz's is the more recent paper.