Harris: The copepod genus Porcellidium 
93 
Key to the species of Porcelloides 
1 Female caudal rami excluded from arch of genital double-somite. 
T3 absent from caudal ramus, y seta 14 way down bevelled edge 
of ramus. Hyaline border of cephalosome not striated. Male 
rostrum keeled. Terminal setae on male P5 short (< 14 length of 
lateral edge of P5). Colour brown. Europe. (Plate 1G, p. 67) 
. Porcelloides tenuicaudus (Claus, 1860) comb. nov. 
- Half female caudal rami included in arch of genital double¬ 
somite. T3 present on caudal ramus, y seta at lateral corner of 
bevelled edge. Hyaline border of cephalosome striated. Male 
rostrum not keeled. Terminal setae on male P5 long ( 2 A length of 
lateral edge of P5). Dorsal patch of red/brown on cephalosome. 
Europe. (Plate IE, p. 67) . Porcelloides scutatus (Claus, 1860) comb. nov. 
Porcelloides tenuicaudus (Claus, 1860) 
comb. nov. 
Figs 17-20 
Porcellidium tenuicauda Claus, 1860: 6-8, taf., II, abb., 
10-18. 
P tenuicauda. —Brady, 1880: 166; Claus, 1863: 149; Claus, 
1889: 32; Norman & Scott, 1906: 182; Pesta, 1935: 374; 
Bocquet, 1948: 239-242; Lang, 1948: 422; Bartsch, 
1987: 139-143; Huys etal, 1996: 307;Bodin, 1997: 65; 
Walker-Smith, 2001: 656; Wells, 2007: 79. 
Porcellidium dentatum. —Claus, 1860. 
Porcellidium ovatum. —Haller, 1879; Haller, 1880: 58. 
Material examined. Specimens inNHM, London andNMI, 
Dublin (see Appendix 1 and 2). Living material was collected 
for dissection and measurement from the sublittoral at Castle 
Head, Dale, Pembrokeshire, Wales (51°42'N 5°10'W) and 
Clachan, Shiel Sound, Oban, Scotland (56°19'N 5°35'W), 
V. A. Harris, 1974, 1987. 
Specimens deposited in NHM, London (1 <$, 4 9° and 
three slide mounted dissections). 
The following re-description is based on specimens 
from Clachan identified from Claus (1860,1863,1889) and 
Bocquet’s (1948) description of Porcellidium tenuicauda 
and P. dentatum. 
Diagnosis. Hyaline border plain (no striations); male rostrum 
with ventral keel (Fig. 20C); female caudal rami excluded 
from arch of genital double-somite, ramus acutely trapezoid, 
apical angle 25°, bevelled edge long (4 x length of lateral 
edge), marginal setules down whole length of medial and 
bevelled edge, T1 and y seta half-way down bevelled edge, 
T3 absent (Fig. 17D); spinous setae on female P4 endopod 
segments 2 and 3 slender, finely serrulate; falciform ridge of 
female P5 a smooth curve (compare Fig. 22E), apical seta 
not pinnate; terminal setae on male P5 short (14 length of 
exopod lateral edge). 
Biometric data. Because animals are not as dorsoventrally 
flattened as other species and tend to conglobate (roll 
into a ball) when preserved, some distortion takes place 
when specimens are mounted flat on a slide. This leads to 
uncertainty in some of the measurements. There is a wide 
difference in body length measured to posterior of genital 
double-somite (L U rs) and the total length measured to the 
extremity of the caudal rami (L m ax). Both measurements 
are given. Claus (1860) gives female length as 114 mm and 
Brady (1880) gives l/23rd inch (1.1 mm). The following 
measurements were made on specimens from Scotland and 
Pembrokeshire, Wales. 
Females (N = 6): maximum length (L m ax)1.04 mm (range 
0.99-1.10 mm), body length (L U rs) 0.89 mm (range 0.87-0.92 
mm); cephalosome width (W) 0.74 mm (range 0.71-0.80 
mm); rostrum width (R) 0.16 mm (range 0.15-0.18 mm); 
genital double-somite width 0.35 mm, length 0.29 mm; 
caudal ramus length 0.19 mm, width 0.07 mm; apical angle 
of ramus 25-30°. 
Ratios: LmaxAV 1.4 (range 1.22-1.42), L ur s/W 1.2 (range 
1.13-1.24); W/R 4.5; genital double-somite width 45% of 
cephalosome width, w/1 1 . 2 , length of posterior lobe 15% 
of lateral border, arch 24% of genital double-somite length; 
caudal ramus 21% of L urs , w/1 2.7, Hicks’ index for a seta 
93%, for (3 seta 81%. 
Males (N = 2): maximum length (L m ax) 1.0, 1,02 mm, body 
length (Lurs) 0.95 mm; cephalosome width (W) 0.80 mm; 
apical angle of caudal ramus 25°; antennule fully extended 
0.22 mm; spermatophore (N = 4 measured on females) 0.29 
x 0.08 mm. 
Ratios: L m ax/W 1.27, L U rs/W 1.2; male antennule (fully 
extended) 28% of cephalosome width, segment 2 32%, 
segment 3+4 34%, dactylus 18% of antennule length; 
spermatophore 30% of body length L U rs. 
Description. Adult females (Fig. 17A; Plate 1G, p. 67): 
colour red-brown partly due to orange oil droplets in body, 
middle of cephalosome darker in some animals. Body 
oviform (egg-shape) in outline, cephalosome semicircular, 
wider (relative to body length) than any other species in the 
family, body not dorsoventrally flattened to the same extent 
as most other species (height approximately 14 cephalosome 
width). Animals can conglobate. Rostrum projects Vs of its 
width. Hyaline border clear (no striations) with eight sensilla 
in plane of membrane, width 15 pm. Ducts of marginal 
glands open dorsal to hyaline membrane. Dorsal surface 
with small pits 4-5 pm in diameter, medial portion of P5 
and dorsal surface of caudal rami ornamented with network 
of ridges (Figs 17D, 19D, 20B). Genital double-somite (Fig. 
17B) narrow, 14 cephalosome width, length about Vs body 
length, posterior lobe short (14 lateral border), not expanded 
laterally, bordered with a few filiform setules, posterior arch 
houses anal somite only, caudal rami completely excluded 
from arch. Genital aperture simple (Fig. 17C). Caudal ramus 
trapezoid, elongate, acute pointed, (1/w = 2.6). Seta T4 large 
