Harris: The copepod genus Porcellidium 
103 
E); terminal setae on male P5 exopod long (>Vi length of 
lateral edge). 
Biometric data. Females (N = 11): maximum length (L m ax) 
0.84 mm, body length (L U rs) 0.78 mm (range 0.74-0.83 mm) 
[female body length from literature 0.75-0.80 mm, Claus 
(1889)]; cephalosome width (W) 0.56 mm; rostrum width 
(R) 0.11 mm; genital double-somite width 0.38 mm, length 
24.5 mm; caudal ramus length 0.135 mm, width 0.075 mm; 
apical angle of ramus 50°. 
Ratios: L max AV 1.52, L urs AV 1.4; W/R 5.1; genital double¬ 
somite width 68% of cephalosome width, w/1 1.54, length 
of posterior lobe 30% of lateral border, arch 40% of genital 
double-somite length; caudal ramus 17% of L urs , 1/w 1.8, 
Hicks’ index for a seta 88%, for |3 seta 72%. 
Males (N = 8): maximum length (Lmax) 0.78 mm, body 
length (L urs ) 0.70 mm; cephalosome width (W) 0.53 mm; 
apical angle of caudal ramus 70°; antennule fully extended 
0.23 mm; spermatophore 0.25 x 0.087 mm (measured on 
female P5). 
Ratios: L max AV 1.47, L U rs/W 1.3; antennule 43% of 
cephalosome width, segment 2 26%, segment 3+4 39%, 
dactylus 28% of antennule length; spermatophore 36% of 
body length (L urs ). 
Description. Adult females (Fig. 21A; Plate IF, p. 67): 
central area of cephalosome and metasome reddish-brown, 
rest of body colourless. Body ovoid in outline, dorsoventrally 
depressed, anterior slightly truncated, rostrum prominent 
with hyaline border, not obscured by anterior bulge of 
cephalosome. Animals do not conglobate. Dorsal pits 
conspicuous, 3-5 pm, area round pits slightly thickened to 
form cuticular network (Fig. 211), very few dorsal sensilla. 
Hyaline border appears to have striations perpendicular 
to edge (Fig. 21G). Striations due to network of ridges 
expanding out above hyaline border (Fig. 21F2, H), hyaline 
border itself is without striations (Fig. 21Fi). Cuticular 
striations 7-9 pm wide, hyaline border 11-13 pm wide (Fig. 
2 IF 2 ). Labrum with central patch of very short setules plus 
group of about eight setules on either side of posterior edge 
(Fig. 22G). Sternum of metasome segment 4 with fimbriate 
setules along posterior border. Genital double-somite short, 
broad (Fig. 2 IB), small lateral notch and area devoid of pits or 
setules marks boundary between anterior and posterior lobes, 
posterior lobe short (A of lateral edge), both lobes fringed 
with fine setules. Posterior arch almost half length of genital 
double-somite, accommodates anal segment and % of caudal 
rami (as far as lateral comer of the bevelled edge). Genital 
opening (Fig. 21C, D). Caudal ramus trapezoid (Fig. 2IE), 
widens slightly posteriorly (maximum width 73 down ramus 
where bevelled edge starts), medial edge without setules, 
T1 pinnate close to y at lateral corner of bevelled edge, T2 
tends to lie almost parallel to bevelled edge, T3 very thin, 
inconspicuous, about 3 x length of terminal setules (difficult 
to see on some animals, Fig. 22H), T4 pinnate at apex of 
ramus, fine setules along bevelled edge between T3 and T4. 
Dorsal surface of ramus with network of ridges. Seta on first 
segment of antennule pinnate. Setation of mouthparts and 
ambulatory limbs typical of family. Antenna (Fig. 22A) with 
filiform setules on basis and segment 1 of endopod, exopod 
with five plumulose setae and one spinous seta, segment 2 
of endopod with proximal setules, one small and two larger 
lateral setae, one plain and one annulate terminal seta, three 
geniculate setae with plain distal portion, terminal claw with 
blunt serrations. Mandible without setules on anterior lobe 
of palp. Maxillule similar to P. tenuicaudus, maxilla (Fig. 
22B), maxilliped (Fig. 22F). PI (Fig. 22C) exopod segment 
1 with single crescentic row of denticles parallel to border, 
endopod with small triangular area of denticles at lateral 
end of fimbriate crescent, endopod 1/w = 1.25. Serrulate 
spinous seta on segment 2 of P3 endopod thin, almost equal 
to length of endopod, large, serrate, spinous seta on segment 
3 longer than endopod (1.5:1), (Fig. 23C). P4 endopod with 
massive, short, serrate, spinous seta on segment 2 and a 
similar serrate seta on segment 3 (Fig. 23B). P5 (Fig. 22D, 
E), dorsal (external) seta on baseoendopod long (40 pm), 
exopod lanceolate with blunt apex (w/1 = 0.26 at level of 
lateral seta), ventral falciform ridge undulating, two pinnate 
dorsal setae, seta at apex pinnate, border setules filiform, long 
(25-30 pm), dorsal surface with network of ridges. Females 
carry 12 eggs in brood chamber (N = 7). 
Adult males (Fig. 24A). Colouration, pits, network and 
striated hyaline border as described for female. Anterior 
outline of cephalosome rounded, slightly truncated with 
small convex projection in midline, lateral angle of antennule 
sockets with conical projection, rostrum V-shaped without 
ventral keel (Fig. 24D). Caudal ramus trapezoid (Fig. 23G), 
width greater than length (1/w = 0.9), medial edge straight, 
lateral edge slightly convex, posterior A of both edges with 
setules, a and (3 setae long ( 3 A width of ramus), terminal setae 
T1-T4 long, all pinnate, T3 larger than on female ramus, 
fringe of fine setules between T3 and T4. Antennule 43% 
of cephalosome width (Fig. 24A), segment 1 with pinnate 
seta, no ventral process on segment 3, segment 4 with 
small serrated triangular proximal denticle, medial large 
denticulate pad, distal denticle with double serrated edge 
(Fig. 24E), segment 5 of dactylus slender, cylindrical, 3 A 
length of segment 3+4, hooked distally (Fig. 24B), segment 
6 small and fused with segment 5. Ambulatory limbs as 
for female except for following. P2 endopod with two 
plumose setae on terminal segment (Fig. 23D). P4 endopod 
segments 2 and 3 with long plumose setae (Fig. 23E). P5 
acutely pointed trapezoid, setae long (% length of lateral 
edge, first (lateral) seta pinnate with row of 7-8 ventral 
setules, remaining setae with 3-5 ventral setules (Fig. 23A). 
Spermatophore reinform with recurrent neck (Fig. 24F). 
Remarks. The animals from Loch Hyne, Ireland, correspond 
to Claus’ description of Porcellidium scutatum. For example, 
they are the same size and colour, the caudal rami are the 
same shape and have the same setation (Claus does not 
show T2, but as pointed out above this is hard to see on 
some specimens) and both have a long cylindrical dactylus 
on the male antennule. But the most compelling reason for 
regarding the two animals to be the same species is the unique 
hyaline border to the cephalosome. Claus states ..surface 
at the edge of the cephalothorax with a clear outer margin 
set through with little rods” (taf.VIII, abb. 18). Figure 21F, 
G, H show the striated border of Porcelloides scutatus. Only 
two other species are known with a striated hyaline border, 
Porcellidium akashimum Harris and Iwasaki (1996a) and an 
undescribed Australian species of Kushia. The false border 
of Tectacingulum tumidum Harris, (1994) is striated, but 
the true hyaline border, which lies on the ventral side of the 
cephalosome, is not striated. 
Superficially, the female of Claus’ Porcellidium scutatum 
