Harris: The copepod genus Porcellidium 
71 
Remarks. The above generic diagnosis is based on animals 
collected from Oban Scotland and identified as Porcellidium 
viride from Brady’s (1880) illustration which shows a species 
specific character of the male antennule. Brady collected 
specimens from the same region of Scotland. 
Fifty-nine species of Porcellidium have been named in the 
literature, but 18 of these cannot be counted as valid species 
for the following reasons. Seven names are synonyms for 
other species i.e., P. dentatum, and P. ovatum for Porcelloides 
tenuicaudus; P. lecanoides and P. sarsi for P. viride; P. 
penicilliferum for Dilatatiocauda tristanensis; P. acutum for 
Kensakia acuta; and P. aoifuchidorum for P. wandoensis , 
three are given to juvenile stages (subrotundum, rotundum, 
australe ) and another eight species cannot be identified 
or placed in a genus because the original description is 
devoid of specific characters, (P. fulvum, P. interruptum, P. 
tuberculatum, P. affine, P. charcoti, P. wolfendeni, P. scotti, 
and P. malleatum), however, some of these may prove to be 
valid species if redescribed in detail. 
This leaves 41 species sufficiently well described to be 
identified and assigned to a genus, though only 20 of these 
can be assigned to Porcellidium on the diagnosis given 
above. The remaining 21 species possess apomorphic 
characters that exclude them from Porcellidium and must be 
transferred to other genera within the Porcellidiidae. 
The genus Porcellidium is not based on apomorphies, but 
on a combination of characters all of which may be found in 
other genera either in an apomorphic or plesiomorphic state. 
Porcellidium rastellum sp. nov. 
Figs 1-3 
Type material. Holotype adult male, length 0.55 mm, 
P81207; allotype adult female, length 0.80 mm, P81208, 
collected from Sargassum sp., sublittoral, Pontoon Rocks, 
Ballina, NSW, Australia, (28°52'S 153°36'E), V. A. Harris, 
1982. Paratype specimens P81209 (20 10 d'c?, 10 
+ juvenile) and paratypes P88552, P88553, P88554, all 
deposited at AM, Sydney. Specimens from the type series 
and Cronulla, Sydney (50 $ $, 30 SS + 50 SS coupled to 
juv. 5), deposited atNHM, London. 
Diagnosis. Female rostrum horizontal bar, (in ventral view 
not V-shaped (Fig. II), anterior edge of cephalosome folded 
ventrally (Fig. 1D), hyaline border not modified; maxilla with 
conspicuous rake-like claw (Fig. 2G); PI exopod segment 1 
with conspicuous crescent of denticulate setules, endopod 
with extensive lateral and medial peg areas consisting of 
minute denticles arranged in rows (Fig. 2E); male antennule 
first seta on segment 2 same length as second seta, no 
plumulose setae on segment 2, segment 3 without ventral 
process, three denticles on segment 4 none are denticulate 
pads; female P5 with broad medial dorsal expansion (Fig. 
1C). Spermatophore elongate, ephemeral on female. 
Biometric data. Females (N = 15): maximum length 
(L max) 0.79 mm, range 0.76—0.81 mm, body length to end 
of genital double-somite (L U rs) 0.77 mm, range 0.74-0.81 
mm; cephalosome width (W) 0.55 mm, range 0.54—0.56 mm; 
rostrum width (R) 0.12 mm; genital double-somite width 
0.28 mm, length 0.19 mm, arch 0.9 mm; caudal ramus length 
0.12 mm, width 0.05 mm. 
Ratios: L urs AV 1.41; W/R 4.6; genital double-somite w/1 
1.5; caudal ramus 15% of L U rs, ramus, l/w2.4, Hicks’ index 
for a 72%, for (3 14%. 
Males (N = 9): maximum length (L m ax) 0.55 mm, body 
length (L U rs) 0.54 mm; cephalosome width 0.45 mm; 
antennule length 0.135 mm. 
Ratios: LursAV 1.2; antennule 30% of Lurs; segment 2 30%, 
segment 3+4 46% and dactylus 23% of antennule length. 
Description. Adultfemales (Fig. 1A; Plate 1A, p. 67): colour 
pale yellow, rostrum a horizontal bar in ventral view (Fig. 
II, not V-shape), wide (W/R = 4.2). The anterolateral edge 
of the cephalosome and hyaline border is folded ventrally as 
far as the second border sensillum, but without modification 
in structure (Fig. ID), hyaline border 8-10 pm wide, 
granular in appearance. Dorsal pits are conspicuous, very 
few dorsal sensilla. Labrum without ridge plates. Genital 
double-somite (Fig. IF) bordered with strong setules, dorsal 
surface pitted, anterior and posterior lobes separated by 
deep notch, posterior lobe rounded, arch about half length 
of genital double-somite. Caudal rami rectangular (Fig. 
IE), dorsal surface with pits, no setules on medial or lateral 
edges, terminal setae pinnate, T1 not recessed, T2 and T3 
close together, T4 set in from medial corner which is slightly 
bevelled, (3 seta close to posterior border, fringe of setules 
on posterior edge between T3 and medial corner (Fig. 1H). 
Structure and setation of ambulatory limbs and mouthparts 
typical of family. Basis of antenna with oblique double row 
of setules (Fig. 2A), endopod segment 2 with three lateral 
setae, end part of geniculate setae plain, terminal claw 
comb-like. Mandible (Fig. 2F) with strong molar process, 
small group of setules on anterior lobe of palp, maxillule 
(Fig. 2C), maxilla endopod with conspicuous rake-like or 
ctenoid claw (Fig. 2G), maxilliped (Fig. 2B) normal. First 
ambulatory limb PI with conspicuous crescent of rod-like 
denticles parallel to edge of exopod segment 1, endopod 
has broad band of denticles down medial edge and a large 
latero-central area of denticles which occupies nearly % 
of the area anterior to the fimbriate crescent, denticles are 
minute and arranged in parallel rows, endopod 1/w = 1.35 
(Fig. 2E). Serrulate spinous seta on P2 endopod segment 3 
almost as long as endopod (Fig. 3A). Serrate spinous seta 
on P3 endopod segment 2 (Fig. 2F) shorter than endopod 
(0.8:1), large serrate spinous seta on segment 3 much longer 
than endopod (1.4:1). P4 endopod segments 2 with straight 
serrulate spinous seta, serrulate spinous seta on segment 
3 J-shape (Fig. 3B). Ventral seta on baseoendopod of P5 
reaches back to level of lateral seta on exopod, P5 exopod 
(Fig. 1C) lanceolate with broad dorsal medial expansion 
which partly covers genital double-somite (Fig. 1A, C), 
there are two sub-apical dorsal setae and one short apical 
seta, dorsal surface of P5 pitted. Females carry eight or 10 
eggs in brood chamber. 
Adult males (Fig. IB) colour, dorsal pits and hyaline 
border as for female. Cephalosome truncated, shoulders 
smoothly rounded, lateral corner of antennule socket not 
prominent, anterior edge of cephalosome and hyaline border 
reflexed ventrally (as in female) but not modified. Dorsal 
surface of genital double-somite pitted. Caudal ramus (Fig. 
1G, J) with bevelled medial corner makes ramus appear 
pentagonal, dorsal surface with pits. Setae as for female with 
P seta close to posterior border, T1 not recessed, T4 set in at 
base of bevelled medial corner, posterior fringe of setules 
extends past T4 along bevelled edge. Antennule (Fig. 2D) 
segment 2 short triangular without plumulose setae, first seta 
not longer than 1.5 times other setae on segment, no ventral 
process or blade on segment 3, segment 4 with three coupling 
