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Records of the Australian Museum (2009) Vol. 61 
Head (Fig. 12B) with pyriform organ posterior to eye 
mound and about as high as latter. Anterior sides of eye 
mound and rostrum both straight and meeting at a distinct 
angle of about 110°. Rostrum elongated triangular, about as 
long as anterior surface of head, apex rounded and slightly 
flexed downward. Naupliar eye triangular, its axis aligned 
similarly to that of rostrum. Length of first antenna subequal 
to that of peduncle of second antenna, and former bearing 
7 lobules. Second antenna with 12 apparent peduncular 
segments and 15-16 flagellomeres on flagella, most middle 
segments with 5-7 spines, 2 of which sometimes grouped 
apically. 
Trunk segments 25 in number, each bearing pair of tho- 
racopods, these decreasing in size posteriorly, and anterior 
two pairs modified as claspers. Posterior dorsal armature 
comprising 1-3 spines on small protuberances on each of 
last 7 segments, and a few setae on preceding 6 segments. 
Claspers of normal structure for Limnadopsis, with one spine 
apically on the movable finger, and prominent, asymmetrical 
protrusion midway along anterior edge of hand. 
Telson (Fig. 12C) with two rows of 13 dorsal spines 
each. Most anterior spine about 1.5 times the size of next 
spine, most posterior spines smaller and sharper than 
anterior spines, and spines in middle of row more widely 
spaced than anterior or posterior spines. Two telsonic setae 
inserted on protuberance situated about one quarter of way 
along dorsal side of telson. Caudal claws about 8 times 
longer than wide, with long, almost straight basal section 
of even width and much shorter, curved apical part tapering 
to a sharp apex. Basally, cercopods bearing about 12 setae 
mediodorsally, most of them being a little longer than width 
of claw, followed by 3 short spines inserted almost dorsally, 
the posteriormost the largest. Curved, tapered apical part of 
cercopods bearing many short denticles dorsally. 
Female. Carapace (Fig. 12D) oval, 11 mm by 7 mm, L:D 
ratio 1.57. Dorsal margin more convex than in male and also 
with distinct depression in umbo area. Dorsal margin largely 
smooth, but minor serrations present posteriorly at junctions 
of growth lines. Growth lines 9, weakly expressed. 
Head (Fig. 12E) typical for females of Limnadopsis , with 
short triangular rostrum. Six lobules on first antenna. Second 
antenna as in male. 
Telson (Fig. 12F) similar to that of male, but with 15 
telsonic spines in each row, and six spines on caudal claws. 
Eggs (Fig. 5J) round, about 175 pm in diameter (range 
170-178 pm; n = 5) with short deep grooves, aligned at 
most in pairs, otherwise set at various angles to one another. 
Intergroove areas smooth and internally frothy. 
Variability. Considerable variability was noted in repre¬ 
sentatives of the six populations studied. Growth lines vary 
from 9 to 12, but they are invariably weakly expressed and 
meet the dorsal margin in at most weak dorsal serrations 
posteriorly. First antennal lobules vary from 6 to 9, with 
males of a given population generally having one more than 
females. On the telson, the dorsal spines vary from 12 to 16 
per row, with a mean of 13; and the spines on the caudal 
claws range from 2 to 6, usually about 4. 
Comments. This species is similar to L. parvispinus. Despite 
wide variation in many features of both species, there are 
many differences between the two, including: (<3) fewer 
telsonic spines in L. occidentalis (about 13-15 per row 
compared to about 18-22); ( b ) A slight anterior depression 
in the dorsal carapace margin of L. occidentalis while in L. 
parvispinus the margin is straight or slightly convex; (c) the 
differently shaped eggs, round in L. occidentalis and with 
the grooves ungrouped or at most in pairs, compared to cy- 
Fig. 12. Limnadopsis occidentalis n.sp., Boolathana Station, via Carnarvon, WA. Male: (A) carapace; ( B ) head; (C) 
telson. Female: (D) carapace; (E) head; (F) telson. For clarity some growth lines of the carapace are incompletely 
shown anterior to umbo. Scale bars 1 mm. 
