178 
Records of the Australian Museum (2014) Vol. 66 
Geddesia quadrata sp. nov. 
Figs 6-9 
Type material. Holotype, adult male, length 0.86 mm, 
P81221; allotype, adult female, length 1.06 mm, P81222 
(both mounted on slide), deposited at AM, Sydney. Paratype 
female mounted on slide and deposited at NHM, London. All 
collected from seagrass {Zostera sp?), Green Island, Great 
Barrier Reef, Queensland, Australia (16°41'S 45°56'E), V. 
A. Harris, 1973. 
Diagnosis. Female cephalosome hemi-ellipse sharply 
truncated, anterior edge straight, clear area (lens) above 
rostrum; male cephalosome deeply concave anteriorly; a 
and p setae on male caudal ramus and terminal setae T1, T2, 
T4, all very short (< % width of ramus); area of denticulate 
setules on PI endopod resemble maize corn cob; male P2 
with two terminal setae on endopod; falciform ventral ridge 
on female P5 exopod with deep posterior (apical) notch; 
female length 1.06 mm, colour yellow. 
Biometric data. Females (N = 4): maximum length (L m ax) 
1.06 mm, body length (L urs ) 0.98 mm; cephalosome width 
(W) mean 0.75 mm; rostrum width 0.16 mm; genital double¬ 
somite width 0.33 mm, length 0.22 mm; caudal ramus length 
0.15, width 0.08 mm. 
Ratios: L U rs/W 1.3, W/R 4.7; genital double-somite w/1 
1.5, arch 50% of length; caudal ramus 15% of L U rs, 1/w 1.8, 
Hicks’ index for a 80%, |3 50%. 
Males (N = 3): length (Lmax) 0.86 mm [0.90 mm*], body 
length (L urs ) 0.81 mm [0.85 mm*]; cephalosome width 0.70 
mm, length 0.47 mm [0.50 mm*]; antennule fully extended 
0.21 mm; spermatophore 0.21 x 0.09 mm. [* = Measured 
from shoulder. Due to the deeply concave anterior border of 
the male cephalosome, the length measured from the rostrum 
is very much shorter.] 
Ratios: LmaxAV 1.2 [1.28 mm] cephalosome length 55% of 
Lmax; caudal ramus 1/w 1.0; antennule 23% of Lmax, segment 
3+4 38%, dactylus 27% of antennule length; spermatophore 
25% of Lmax- 
Description. Adult females (Fig. 6A; Plate ID, p. 172): 
colour lemon yellow, cephalosome hemi-ellipse strongly 
truncated anteriorly with small epaulette at shoulder, rostrum 
prominent (Fig. 6B, C) with clear lens-like structure dorsal 
to rostrum. Dorsal pits very small (2 pm) near edge of 
cephalosome, hyaline border clear, 15 pm wide (Fig. 1C). 
Labrum without setules or ridge plates. Genital double¬ 
somite (Fig. 7D) narrow (less than !A width of body), very 
small notch marks boundary between anterior and posterior 
lobes (Fig. 7F marked with *), posterior lobe about % length 
of anterior lobe, acutely pointed posteriorly, lateral edge with 
very short border setules, arch less than !4 length of genital 
double-somite. Genital opening (Fig. 6F). Caudal ramus (Fig. 
6E) pentagonal, widens posteriorly, maximum width 2 A down 
ramus, dorsal surface with fine reticulation. Bevelled edge 
with setules, posterior edge straight, 3 A of maximum width, 
90° to medial edge, posterior border setules conspicuous. 
Beta seta half way down ramus, T1, and y close together near 
posterior end of bevelled edge, T3 absent, T4 small at medial 
corner. Structure and setation of mouthparts and ambulatory 
limbs typical of family. Antenna (Fig. 7A, B) with fine setules 
along edge of basis and endopod segment 1, exopod with five 
plumulose setae and one serrulate spinous seta, geniculate 
setae on endopod segment 2 with plain terminal section, 
claw comb-like. Setae on mandible endopod unusually long 
(Fig. 7D). Maxillule with six setae on endopod. Claw on 
maxilla with distal edge comb-like (Fig. 7H). Maxilliped 
(Fig. 7E). PI (Fig. 8F), exopod segment 1 with single row 
of denticles parallel to edge, endopod segment 1 short, broad 
(w/1 = 0.9) with elongate patch of denticulate setules that 
resemble maize corn cob at lateral end of fimbriate crescent. 
Setules along external edge of segment 1 on P2, P3 and P4 
exopods unusually strong (Fig. 8A, C, D). Serrate spinous 
seta on segment 2 of P3 endopod strong, almost as long as 
endopod (0.9:1), large serrate spinous seta on segment 3 
longer than endopod (1.35:1, Fig. 8A). Seta on endopod of 
P4 segment 2 and internal seta of segment 3 strong serrulate 
spinous setae l A length of endopod (Fig. 8D). P5 exopod 
(Fig. 6G) lanceolate, apex rounded (not acute), apical end 
of ventral falciform ridge terminates in notch (Fig. 7G), two 
dorsal and one apical seta present (not pinnate), P5s extend 
beyond genital double-somite but are separated by full width 
of caudal rami. Females carry six eggs. 
Adult males (Fig. 9A), colour lemon yellow, cephalosome 
truncated hemi-ellipse, posterior half of body semi-circular. 
Anterior of cephalosome strongly concave, convex medial 
prominence above rostrum with clear, lens-like, structure in 
rostrum (Fig. 9D), small epaulette present (Fig. 9B). Dorsal 
pits and hyaline border as for female. Caudal ramus (Fig. 
8B) square (1/w = 1), dorsal surface with reticulate markings, 
lateral edge slightly convex with border setules along 
posterior half, a and (3 setae about % width of ramus or less, 
|3 seta half way down ramus. Medial corner 90° with T4 at 
corner, setae T1 and y recessed at lateral corner (no bevelled 
edge), T3 absent, posterior border straight with conspicuous 
row of setules, distance between T2 and T4 80% of ramus 
width. Antennule (Figs 9E, F) without denticle or comb 
on segment 3, prominent peg-like ventral process present 
(marked * on figures), segment 4 with two small serrated 
denticles and two bulbous structures (Fig. 9E, F). Dactylus 
cylindrical, as long as segment 3+4.Two plumose terminal 
setae on P2 endopod (Fig. 8E), setae on P4 endopod plumose 
(not spinous). P5 exopod (Fig. 9C) trapezoidal, lateral seta 
same size and shape as five terminal setae, row of 20 ventral 
setules, no setules at base of terminal setae. Spermatophore 
% length of body. 
Etymology. The specific name refers to the straight posterior 
border of the caudal ramus which makes an angle of 90° with 
the medial edge, (L. quadratus = made square). 
Remarks. The female animal described by Geddes (1968) 
as Porcellidium trisetosum lacks the T3 seta on its caudal 
ramus and the female cephalosome is truncated anteriorly: 
two features that exclude it from the genus Porcellidium. The 
male antennule is not described, but the maxillule is stated to 
be the same as Sars (1904) described for P. fimbriatum , which 
has six setae on the endopod. Therefore, Geddes’ trisetosum 
fits the diagnosis of Geddesia and should be moved to that 
genus as Geddesia trisetosa (Geddes, 1968) comb. nov. 
The latter differs from G. quadrata in the following 
features: size of female (L ma x0.78 mm), colour (red-brown), 
male P2 endopod with three terminal setae, female Hicks’ 
index for a 70%, length of spinous setae on female P4 
endopod as long as endopod, male P5 with setules at base 
of each terminal seta. 
