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Records of the Australian Museum (2009) Vol. 61 
whorls in large specimens”. There is also S. paumotanus 
(Chamberlin, 1919) dealt with later in this account, in which 
radioles are shown to be arranged in a circle in juveniles, but 
with up to 5 spirals in adults. 
In a cladistic analysis Pillai (2008: 45) showed that 
according to criteria previously employed to separate the 
three genera, they belong to a cohesive group in which 
Pomatoleios is sister to the clade consisting of Pomatoceros 
& Spirobranchus. As a follow-up in the present paper, 
however, Pomatoceros and Pomatoleios are synonymized 
with Spirobranchus for the foregoing reasons. 
Terminology relating to 
collar chaetae in Spirobranchus 
The terminology hitherto used to describe collar chaetae 
of Spirobranchus poses some problems. As discussed 
earlier, the collar fascicle in serpulimorph polychaetes 
consists of two kinds of chaetae, special collar chaetae 
which are modified in various ways and are important 
in the taxonomy of its species, as well as those that end 
distally in simple blades. Where the special collar chaetae 
possess a recognizable boss and a blade, they have been 
termed bayonet-shaped or Spirobranchus-iypt. However, 
the latter descriptive term becomes inapplicable for the 
genus Spirobranchus as a whole since there is a complete 
range from bayonet-shaped to simple blades in the various 
species, as shown in this paper. 
The second type of collar chaetae as well as those of the 
remaining thoracic segments have been termed “hooded 
chaetae”, among others, such as simple limbate chaetae, 
simple bladed chaetae and bladed capillaries. However, if we 
are to define chaetae in relation to the Polychaeta as a whole, 
truly hooded chaetae, aptly termed “soies encapuchonnees” 
in the French literature, are found in certain other polychaete 
groups, such as the Spionidae and the Capitellidae, but absent 
in serpulimorphs. As to be expected, the “hoods” of hooded 
chaetae have an opening on one side in the former taxa, 
unlike in those described as hooded chaetae in sabellids and 
serpulimorphs. The terminology of serpulimorph chaetae is 
under review (ten Hove, personal comm.). 
Abdominal neurochaetae of Spirobranchus have been 
described as having flattened trumpet-shaped ends with 
one side drawn into a long tapering process. However, 
these ‘trumpet-shaped’ ends gradually become reduced to 
such an extent that although they appear to be capillaries 
towards the posterior end of the abdomen, they are actually 
narrowly bladed at their tips, as also seen in many other 
serpulid genera. 
Section 1: The Kimberleys’ species of Spirobranchus 
Spirobranchus baileybrockae n.sp. 
Fig. 37A-H 
Material examined. Kimberleys, Western Australia, holotype lacking its 
tube, AM W21421; sandy cay on Port George IV, 15°20'S 124°39'E, 12 
Jul. 1988, st 26; coll. PA. Hutchings. 
Description 
Measurements. Total length 16.6 mm; width of thorax 2.5 
mm; length of operculum and peduncle 6.0 mm; length of 
shortest opercular horn (occurring dorsally) 2.0 mm, longest 
horn (occurring ventrally) 2.3 mm; length of abdomen 7.9 
mm; number of abdominal segments 65. 
Tube. Missing. 
Worm. Radioles colourless and translucent, thorax and 
abdomen opaque and colourless; opercular plate white, 
with a translucent rim, its horns white with transparent 
medial and lateral spines; operculum on left, rudimentary 
operculum absent; opercular plate circular, bearing a circle 
of 8 very long horns and a short central process (Fig. 
37A-C). Each long horn bears a row of somewhat long 
usually 3, sometimes 4, pointed medial spines, and short 
lateral spines (Fig. 37C); medial spines unbranched, those 
towards the base comparatively longer and hooked towards 
the centre; lateral spines may bear 2 or 3 smaller spines. 
Peduncle winged, wings unfringed (Fig. 37A,B). Radioles: 
23 on each side, arranged in a circle, their pinnule-free tips 
short and thick, pinnules very fine. Inter-radiolar membranes 
unfringed. Collar large, its ventral lobe triangular, lateral 
lobes rounded and reach third or 4th thoracic chaetiger; 7 
thoracic chaetigers; apron present. 
Chaetae. Special collar chaetae bayonet-shaped (Fig. 
37D,E), lack an unserrated notch; a rasp-like area of the 
chaetal shaft precedes the boss; chaetal blade longer than 
serrated part of shaft plus boss; serrations along distal part of 
chaetal shaft ventral and ventrolateral. Thoracic uncini saw¬ 
shaped (Fig. 37F), with 12 or 13 teeth and an anterior gouged 
process; anterior abdo min al uncini (Fig. 37G) similar but 
smaller, with about 10 teeth; posterior abdominal uncini (Fig. 
37H) still smaller, bear about 12 teeth. Abdominal chaetae 
with long shafts protruding prominently from abdominal wall 
occur from first abdominal segment onwards. 
Remarks. Spirobranchus baileybrockae n.sp. is identical 
with regard to all the important characters of the worm 
described by Bailey-brock (1985: 204, fig. 8a-f) from Fiji 
as variant forms of Spirobranchus tetraceros (Schmarda, 
1861). Although the latter were not examined in this study, 
Bailey-Brock’s very good descriptions of the two Fijian 
specimensare adequate for the discussion and conclusions 
which follow. Firstly, although the tube of the Kimberleys 
holotype is missing, Bailey-Brock’s description of it in two 
specimens is in contrast with that of S. tetraceros. In the 
larger of the two, tube colour is “salmon-pink with a faint 
rose tinge to the anterior part of median ridge”; in the smaller 
specimen, the earlier formed part of the tube is white, “vivid 
rose-pink” along the median longitudinal ridge and extending 
anteriorly towards the aperture. As regards tube shape, that 
of the larger specimen is triangular in cross-section, has 
broad lateral flanges, and a well-formed sinuous median 
