Dilatatiocauda dilatata ( Hicks, 1971 ), 2002

Harris, V. A., 2002, A New Genus Belonging to the Family Porcellidiidae (Crustacea: Copepoda: Harpacticoida) With Three New Species from Australia, Records of the Australian Museum 54, pp. 1-24 : 2

Dilatatiocauda dilatata ( Hicks, 1971)

Figs. 1, 2 & 3

Porcellidium dilatatum Hicks, 1971 , 94–98, figs. 5–7.

Type material. Collected from Island Bay , Wellington, Aotearoa ( New Zealand), G. R. F. Hicks (see under Distribution and abundance below) .

Diagnosis. Adult female: comb plates on labrum with numerous ridges (>8); sternal plate of metasomal segment 4 with ridges, not fimbriate; caudal rami rectangular (L/W ratio 3.8), seta proximally inserted (¼ way down ramus), terminal setae T2 & T4 large, equal in size, pinnate, seta T3 plain, very thin, seta T4 set in from medial corner (1 5 width); longest geniculate seta on antenna not longer than endopod segment 2, terminal part straight, plain; large lateral area of peg-like denticles on P1 endopod (>½ width of endopod), no denticulate pegs along medial border; P4 endopod segments not fused; no chitinous striations along anterolateral edge of female P5. Adult male: coupling denticles of antennule small, not conspicuous; P2 with two plumose terminal setae on endopod; P5 setae unipinnate deltoid, row of ventral setules at base of each terminal seta.

Dimensions. Female *: length 0.92 mm (rostrum to posterior tip of urosome), cephalosome width 0.58 mm, length to width ratio 1.6. Rostrum 0.18 mm wide, ratio of body width to rostrum 3.2. Urosome width to length ratio 1.2. Caudal ramus length to width ratio 3.8; dilation index 10.3 ([distal width–proximal width]/length × 100). Male *: length 0.63 mm, width 0.46 mm, body length to width ratio 1.4. (* Measurements taken from single paratype specimens of male and female.)

Description. Adult female. Anterior outline of cephalosome semicircular, rostrum prominent, with hyaline border, projects about ¼ of its width. Dorsal surface ornamentation of pits indistinct except for three or four rows of pits tangential to anterior edge of cephalosome ( Fig. 2A), no patches of honeycomb-like ridges on dorsal surface, hyaline border 13 µm wide, granular. Comb plates on labrum ( Fig. 1C) with numerous ridges (>8). Sternal plate of metasomal segment 4 not fimbriate (i.e., without hair-like setules), ornamented with numerous ridges running parallel to body axis ( Fig. 2F). Urosome broad ( Fig. 2E), very small notch and indistinct scar mark boundary between anterior and posterior lobes, anterior lobe without marginal setules, posterior lobe with strong, lanceolate marginal setules, one sensory seta on posterior border. Caudal arch deep (58% of urosome length). Caudal rami ( Fig. 1B) elongate, rectangular, expanding distally, terminal border straight except for slight bevel at medial corner. Alpha seta proximal (situated about ¼ way down ramus). Hicks’ index (distance