Capa & Murray: Australian Megalomma sabellid polychaetes 
215 
Table 1. Variation 
of number of chaetigers, pairs of eyes and radioles on M. interrupta 
n.sp. 
site 
thoracic 
abdominal 
number radioles 
number of 
distribution of 
chaetigers 
chaetigers 
(pairs) 
eyes (pairs) 
radiolar eyes 
AM W35480 
8 
91 
13 
2 
1,X 
AM W35481 
8 
— 
10 
3 
1,5,6 
AM W35479 
10 
— 
18 
2 
1,5 
AM W35479 
8 
83 
16 
3 
1,6,7 
AM W35479 
10 
— 
13 
4 
1,6-8 
AM W35479 
8 
69 
11 
6 
1,4-8 
AM W35479 
8 
73 
12 
1 
1 
AM W35482 
8 
>100 
16 
5 
1, 7-10 
AM W35483 
8 
— 
14 
3 
1,4,5 
AM W35485 
8 
— 
13 
4 
1,6-8 
AM W35485 
8 
— 
14 
3 
1,8,9 
AM W35485 
8 
c. 100 
14 
3 
1,8,9 
AM W35486 
8 
— 
9 
5 
1,6-9 
AM W35487 
8 
— 
12 
5 
1, 7-10 
AM W35488 
8 
118 
10 
1 
1 
AM W35488 
8 
104 
11 
2 
1,4 
AM W35488 
8 
81 
13 
3 
1,8-9 
AM W35488 
8 
— 
11 
1 
1 
AM W35488 
8 
84 
11 
3 
1,7,8 
AM W35489 
8 
— 
13 
4 
1,5-7 
AM W35496 
8 
— 
14 
4 
1,6-8 
AM W35498 
9 
— 
15 
5 
1,8-11 
AM W35498 
9 
— 
15 
2 
1,9 
AM W35497 
8 
— 
14 
3 
1,5,6 
MAGNT W5975 
8 
— 
18 
8 
1, 6-12 
Number of eyes (pairs) / number of radioles (pairs) 
Figure 9. Graph representing the variety of number of pairs of 
eyes against the number of pairs of radioles in Megalomma inter- 
rupta n.sp. 
and ventral sacs present (Fig. 10A). Caruncle absent. Smooth 
keel present between dorsal lips (Fig. 10B). Posterior 
peristomial collar with rounded dorsal margins and with 
wide gap between them but with low fleshy ridges that 
continue obliquely from middorsal faecal groove to vestigial 
pockets, pockets level with notochaetae of first chaetiger 
(Fig. 10B); lateral margins of collar smooth, perpendicular 
to body axis and covering the junction of thorax and crown; 
ventral lappets prominent, rounded and overlapping (Fig. 
10A). Ventral shields quadrangular, all similar in width down 
the body, almost in contact with the neuropodial tori (Fig. 
10A). First ventral shield longer than the rest, with m-shaped 
anterior margin although not conspicuous. First chaetiger 
with about 20 superior and inferior elongate narrowly hooded 
notochaetae, superior longer than inferior. Chaetigers 2-8 
with about 20 elongate narrowly hooded superior chaetae 
and 20-25 broadly hooded inferior chaetae (Fig. 10C-E) 
(type B). Neuropodial tori slightly diminishing in width 
posteriorly. Thoracic uncini with several rows of small 
teeth, similar in size, above main fang (Fig. 10F); uncinus 
with well developed breast, handle similar in length to the 
distance from breast to main fang. Companion chaetae 
with asymmetrical membrane and small teeth covering 
most of its surface (Fig. 10H). Neuropodia of anterior 
abdominal chaetigers with broadly hooded chaetae (Fig. 
101). Abdominal notopodia with uncini similar to thoracic but 
with shorter handles (Fig. 10G). Pygidium bilobed, eyespots 
absent. Chitinous hard tube (specimen MAGNT W17356), 
covered with fine sand on anterior third of length. 
Variation. The other specimens have eight thoracic 
chaetigers and 15-25 radioles on each branchial lobe. 
Specimens possess one to three pairs of subdistal radiolar 
eyes, and some have eyes missing on the third dorsalmost 
radioles, in which case they are present on the fourth pair; 
relative size of eyes varies from one specimen to another—in 
some the two dorsalmost pairs are large and the third pair 
significantly smaller, while in others the difference in size 
is more gradual, diminishing ventrally. The specimens also 
vary in the size of the gap between ventral shields and tori. 
In some specimens the ventral lappets do not overlap. 
