Capa & Murray: Australian Megalomma sabellid polychaetes 
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dorsal collar margins not fused to faecal groove, presence 
of vestigial pockets (according to original description by 
Knight-Jones, 1997), and eyes on dorsalmost radioles. The 
differences between the two species are that the specimens 
from Australia bear eyes on other radioles, and also, using a 
perhaps more significant species-character, that the inf erior 
thoracic chaetae have progressively tapering distal tips (type 
B) in the specimens described herein, whereas they narrow 
abruptly (type A) in M. kaikourense. 
Megalomma inflata n.sp. 
Figs 4G,H, 5D, 11 
Material examined. New South Wales. Holotype AM W35503, 
southeast of Bate Bay, 34°04'S 151°13'E, coll, by The Ecology Lab for 
RMI/Pioneer Project, 15 Jan. 1990,45-50 m, Stn RMIC26. Paratypes: 
AM W35504 (1 spec.), east of Bass Point, 34°36'S 150°54E, 25 Jun.-26 
Jul. 1990, 45-50 m, Stn RMI BP51; AM W35505 (2 spec.), east of Bass 
Point, 34°36’S 150°54E, 3-18 Jan. 1991, 65-70 m, Stn RMI 4/236; AM 
W35506 (1 spec.), east of Bass Point, 34°36’S 150°54E, 25 Jun.-26 Jul. 
1990, 45-50 m, Stn BP43; AM W23057 (1 spec, on SEM stub), east of 
Bass Point, 34°36'S 150°54E, coll, by The Ecology Lab for RMI/Pioneer 
Project, 1 Feb. 1990,25-50 m. AMW35753 (1 spec.), south of Batemans 
Bay, south side of Burrewarra Point, 35°50'16"S 150°14’05"E, 28 Mar. 
2004, 17 m, from algal and bryozoan (cf. Amathia) turf on vertical rock 
face, coll. Australian Museum party, Stn NSW 2631. 
Additional material. Megalomma quadrioculatum, holotype ZMUH PE 
1303, Aripu Coral Reef, Sri Lanka, coll. Willey, 1905. 
Diagnosis. The synapomorphy of this species is the 
presence of an inflated peristomium protruding from collar. 
Moreover, M. inflata n.sp. is characterized by a combination 
of characters: dorsalmost radioles with large subdistal 
compound eyes and occasionally one or two small pairs in 
following radioles, radiolar skeleton with around 10 cells 
in transverse section, dorsal margins of collar fused to the 
faecal groove forming broad and U-shaped pockets on each 
side, caruncle absent, and thoracic inferior chaetae with tips 
progressively tapering (type B). 
Description. Holotype complete and in good condition 
measuring 22 mm long and 2 mm wide, with eight thoracic 
chaetigers and 37 abdominal chaetigers. Crown longer than 
thorax, with 14 pairs of radioles arranged in two semi¬ 
circular lobes. External margin of radioles quadrangular, 
lateral flanges absent (Fig. 11 A), skeleton with 8-10 cells in 
transverse section (Fig. 5D). Tip of radioles digitiform and 
shorter than pinnules (Fig. 11 A). Three pairs of dorsalmost 
radioles with a subdistal compound eye and an extra fourth 
eye on the right side, with distinct ommatidia, eye-size 
diminishing ventrally; dorsalmost eyes spiral, almost 
surrounding radioles. Dorsal lips with radiolar appendages 
shorter than two thoracic chaetigers and no visible pinnular 
appendages. Ventral lips rounded and well developed. 
Ventral sacs present. Caruncle absent. Short smooth keel 
present. Posterior peristomial collar with rounded dorsal 
margins fused to faecal groove, dorsal collar lappets absent 
(Fig. 11C); collar pockets present, low due to deep incision 
(dorsal peristomium inflated and dorsal collar difficult 
to discern) (Fig. 11C); lateral margins of collar smooth, 
ventral lappets prominent, pointed and not overlapping 
(Fig. 11B,C). Ventral shields quadrangular, separated 
from the neuropodial tori, all similar in width (Fig. 11B). 
First ventral shield longer than the rest, with m-shaped 
anterior margin although not conspicuous. First chaetiger 
with superior and inferior elongate narrowly hooded 
chaetae, superior longer than inferior (Fig. 11D). Rest of 
thoracic chaetigers with elongate narrowly hooded superior 
chaetae and broadly hooded inferior notochaetae with tips 
progressively tapering (type B) (Fig. 11E,G). Neuropodial 
tori slightly diminishing in width posteriorly. Thoracic 
uncini with several rows of small teeth, similar in size, 
above main fang (Fig. 11H); uncinus with well developed 
breast, handle twice length of the distance from breast to 
main fang (Fig. 4G). Companion chaetae with asymmetrical 
membrane and teeth covering about half the length (Fig. 
111). Neuropodia of anterior abdominal chaetigers with 
narrowly hooded chaetae (Fig. 11F). Notopodia with 
uncini similar to thoracic uncini (Fig. 11J) but with shorter 
handles (Fig. 4H). Pygidium trilobed from ventral view, as 
a rounded papilla from dorsal view, with scattered eyespots 
laterally. Tube made of a thin and flexible layer of mucus 
covered by a mixture of fine sediment and mud. 
Variation. The paratypes range in size from 10-25 mm in 
length. The number of pairs of radioles varies from eight to 
ten. They possess one to two pairs of radiolar eyes (although 
the holotype possesses 3 pairs plus an extra eye on one side). 
One paratype (from AM W35505) also possesses dark, 
slightly inflated spots on the inner subdistal sides of most of 
the rest of the radioles (excluding the ventralmost three pairs) 
which could be incipient eyes. However, ommatidia could not 
be detected, and these therefore may just be pigmented areas. 
Colour pattern. Pigment occurs at the base of radioles and 
in a few transverse irregular bands in radioles and pinnules. 
Body unpigmented. 
Etymology. The name of this species is related to the 
conspicuously inflated peristomium. This feature is unique 
among other Megalomma species. 
Remarks. This new species displays similar features to 
another species described in the Indo-Pacific area, M. 
cinctum from Taiwan—the fusion of dorsal collar margins 
to the faecal groove, the presence of dorsolateral pockets 
and the distribution of compound eyes in 1-3 dorsalmost 
pairs of radioles (this is if the spots found in one specimen 
are not considered as eyes). However M. inflata n.sp. is 
distinguished from M. cinctum by the conspicuous inflation 
of the peristomium shown in all the specimens, the deep 
U-shaped dorsolateral incisions of the collar (absent in M. 
cinctum ), the presence of well-developed ventral sacs (absent 
in M. cinctum ) and the narrowly hooded shape of the inferior 
thoracic chaetae (or at least slender and thin), but broadly 
hooded (type A) in M. cinctum. 
There are species described from several localities around 
the world that share with this new species some features such 
as the development and shape of collar dorsal margins, collar 
margins fused to the faecal groove, the presence of pockets, 
eyes present on one to three dorsalmost pairs of radioles, and 
the absence of a caruncle. These are M. coloratum (Cham¬ 
berlin, 1919) from California, M. modestum (de Quatre- 
fages, 1866) from Peru, M. roulei (Gravier, 1908) and M. 
splendidum (Moore, 1905). None of these species have an 
inflated peristomium, nor are their collar pockets as broad 
and U-shaped as M. inflata n.sp. Another species described 
from the Indian Ocean and which shares some features 
