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9E). Structure and setation of mouthparts and ambulatory 
limbs typical of family except that segment 3 of P2, P3 and 
P4 exopod has only two spine-like external setae (Figs 11 A, 
B, D, G). Antenna basis without seta (cf. male), exopod with 
five plumulose setae and one finely serrulate spine-like seta, 
geniculate setae on endopod with plain terminal segment, 
terminal claw with fine comb (Fig. 10A). Mandible (Fig. 
10B), maxillule endopod with six setae (Fig. 10E), maxilla 
(Fig. 10F), coxae of maxillipeds touch in midline, basis with 
fimbriate process (Fig. 10C). First segment of PI exopod 
with crescent of denticulate setules (Fig. 10D, left side), first 
segment of endopod broad (1/w = 1.1), area of denticulate 
setules at lateral end of fimbriate crescent, first claw on 
terminal segment comb-like with recurved teeth, second claw 
lamelliform (Fig. 10D). Serrulate spinous seta on segment 3 
of P2 endopod more than Vi length of endopod (0.6:1, Fig. 
11G). Serrate spinous seta on segment 2 of P3 endopod % 
length of endopod (Fig. 11 A), large serrate spinous seta on 
segment 3 longer than endopod (1.38:1). P4 (Fig. 11D) seta 
on endopod segment 2 and first internal seta of segment 3 
plain spinous. P5 exopod (Fig. 9C, 11E) broad, lanceolate 
with blunt apex, ventral falciform ridge terminates in a deep 
indentation or notch that appears to fit round the end of the 
caudal ramus on some specimens (Fig. 9C), medial edge 
of P5’s dorsal expansion overlaps genital double-somite 
extensively, ventral expansion absent, only one sub-tenninal 
dorsal seta present, dorsal pits absent from P5, lateral border 
with double row of setules (ventral row of triangular setules 
and dorsal row of short filiform setules (Fig. 1 IF). Females 
carry four large eggs. 
Adult males (Fig. 12F; Plate 1H, p. 163). Colour lemon 
yellow. Outline of cephalosome a truncated hemi-ellipse, 
deeply concave anteriorly with small medial bulge. 
Cephalosome unusually long ( 2 A body length). Posterior 
region of body (metasome plus genital double-somite with 
P5s) semicircular. Epipleural lobes of third metasome 
segments very long, they wrap round P5s plus caudal rami 
and extend back as far as the posterior limit of the body 
(Fig. 12F, H). Rostrum not keeled ventrally, dorsal pits and 
hyaline border (Fig. 12E) as for female. Caudal rami (Fig. 
12A) not fused to anal segment, more or less rectangular, 
medial edge concave leaving an opening between the rami, 
lateral edge slightly convex, posterior border straight. T1 
absent, y seta recessed at lateral corner, T2 and T3 small, 
very close together, T4 at medial corner, fringe of short 
setules along posterior border between T3 and T4. Fimbs as 
described for female except for the following differences. 
First segment of antennule with pinnate seta (Fig. 12B), 
second segment short, very narrow posteriorly (Fig. 12D), 
segment 3+4 unusually long (> Vi total length of antennule), 
ventral process or blade present, two small tooth-like and 
one rounded coupling denticle present on segment 4 (Fig. 
12G), no denticulate pad or brush-pad present, aesthetasc and 
o seta short (about length of segment 3+4), dactylus broad, 
very short (% length of segment 3+4). Antenna with seta at 
distal end of basis (Fig. 10A, (absent in female). PI as for 
female, P2 with two plumose terminal setae on endopod 
(Fig. 1 IB), P3 similar to female but terminal serrate seta on 
endopod is S-shaped and equal to length of endopod (Fig. 
11C). P5 baseoendopod fused with metasome segment 4 and 
genital double-somite. Exopod of P5 appears to articulate 
with fused genital somite (Fig. 12H), exopod ovate with 
one plain lateral seta half way down lateral edge (Fig. 12C) 
and row of 15+ ventral setules, two microscopic spinules 
(representing atrophied terminal setae) near apex (Fig. 12C). 
Spermatophore very small (Fig. 12F). 
Etymology. Synurus ctenocheirus has been named from the 
unique condition of the first terminal comb-like seta on PI 
endopod. In all other members of the Porcellidiidae both 
claws are lamelliform, Harris and Robertson (1994), but in 
adult and late stage copepodids of this species the first claw 
is comb-like (G. ctenos = a comb + cheiros = hand). 
Remarks. Synurus ctenocheirus is remarkable for four 
unique sexually dimorphic features: presence of a seta on 
basis of male antenna, epipleural lobes of male metasomal 
segment 3 that extend back to the same level as the P5 
limbs, fusion of male M4 with genital double-somite and 
P5 baseoendopod, and fusion of female caudal rami with 
the anal segment. 
Animals named Porcellidium unicus by Ummerkutty 
(1970), although not fully described, clearly belong to the 
genus Synurus by virtue of the oval male P5 with atrophied 
setae, only two external setae on P2, P3 and P4 exopod 
segment 3, and the fusion of male genital double-somite 
with P5 baseoendopod and M4, but these features exclude 
the species from Porcellidium. It should be renamed Synurus 
unicus (Ummerkutty, 1970) comb. nov. 
The following characters distinguish S. unicus from S. 
ctenocheirus. It is larger (female 0.75 mm, male 0.63 mm), 
Hicks’ index for (3 is 50%, the distance between a and (3 setae 
is 'A ramus length and the female caudal ramus is not fused 
to the anal segment. The male P5 is described as pentagonal 
bordered with setules on lateral edge as far as the lateral 
seta and there are three atrophied terminal setae. Synurus 
unicus was collected from algae off Vedalai in the Gulf of 
Mannar, Sri Fanka. 
Distribution. The type series GI2,9/73 (comprising 44 
30 SS + 23 juveniles) was collected from Zostera capricomia 
growing on coral sand in the sublittoral fringe at Green Island, 
Great Barrier Reef, Cairns, but it has not been recorded 
from the southern coast of Queensland (25 °S), V. A. Harris, 
1973. Specimens of this species collected from Okinawa, 
Japan (approx. 27°N) in the collection of Yuka Sasaki have 
been examined by the author. They appear morphologically 
identical to the Australian material. Their size falls within the 
range given above (Yuka Sasaki, pers. comm.). 
