Pillai: Serpulid polychaetes from the Australian Kimberleys 
171 
Spirobranchus maldivensis Pixell, 1913 
Fig. 52B-I 
Spirobranchus maldivensis Pixell, 1913: 81, pi. 8, fig. 7. 
Material examined. Syntypes: BMNH 1924.6.13.114: 3 specimens 
occurring alongside and attached to each other, coll. C. Crossland, labelled 
syntypes, type material of Spirobranchus maldivensis Pixell (1913). 
Additional material examined. BMNH 1939.9.2.554-556, several 
specimens on a shell, from the Gulf of Oman. 
Description 
Measurements. From one of Pixell’s types, as follows: total 
length 19.5 mm; length of operculum and peduncle 6.0 mm; 
long diameter of operculum 2.0 mm. Operculum plus 27 
radioles on left side, no rudimentary operculum on right; 
28 radioles on right side. Length of abdomen: 11.0 mm; 
number of segments 52. 
Tube. In type specimens, caramel to faintly pinkish in 
colour, with slightly darker pink along median longitudinal 
ridge; latter prominent, with conspicuous forwardly 
directed projections which may be triangular towards the 
middle of tube, or end in laterally flattened tips with their 
stumpy ends appearing as if they were broken off. They 
are low anteriorly, and the median longitudinal ridge itself 
may be somewhat sinuous. All three types present on 
one of the tubes (Fig. 52B). Tube colour of specimens in 
additional material examined, BMNH 1939.9.2.554-556, 
range from light caramel to brownish and pink. Some have 
a pair of light brown longitudinal bands along each flank 
and a pinkish colour along the median longitudinal ridge. 
Otherwise, the form of the tubes and other characters agree 
with those of the type specimens. 
Worm. Operculum in type material on left side; no 
rudimentary operculum on right; opercular plate circular, flat, 
lacks processes but shows concentric circular markings (Fig. 
52E); peduncular wings broad and unfringed; 27 radioles on 
the left, 28 on the right in one specimen, arranged in a circle 
on each side; inter-radiolar membranes unfringed. One or two 
whitish patches present at the base of each radiole; uncertain 
whether they represent eyespots or mere pigment patches in 
the preserved material. Thorax: slender, its uncinal tori not 
borne on conspicuous pads (Fig. 52C,D,F). 
Chaetae. Bayonet collar chaetae (Fig. 52G) differ from 
those of other species of Spirobranchus hitherto described in 
this account in being slender, their serrations comparatively 
inconspicuous along the blade, the boss and the serrated 
part of the shaft preceding the boss. Thoracic uncini: saw¬ 
shaped (Fig. 52H), with about 12-13 teeth, in addition to 
the anterior gouge; anterior and posterior abdominal uncini 
similar, the former (Figs 52J) with about 10-11 teeth, and 
the latter about 10-12. 
Remarks. Spirobranchus maldivensis can be recognized 
from most other species of Spirobranchus by its simple 
circular opercular disc, which is devoid of processes, the 
arrangement of its radioles in a circle, unfringed peduncular 
wings and inter-radiolar membranes, the form of its bayonet 
collar chaetae, and the caramel to pinkish colour of its tube. 
The concentric circular markings on the opercular plate are 
clearly not scars left by opercular horns that had become 
detached; horns of Spirobranchus species are not deciduous 
and, if broken off, leave the basal remnants of their horns 
or a conspicuous “wound” marking the place from which 
the horns were broken off. 
Spirobranchus murrayi n.sp. 
Fig. 53A-G 
Material examined. Syntypes: 2 specimens without their tubes, South 
Arabian coast, Gulf of Oman, BMNH 1937.9.2.550-553, depth 106 m, otter 
trawl, Murray Expedition Stn. 71, date 26 Nov.33, labelled specimen Nos. 
1 & 2 by present author. 1 specimen, South Arabian coast, Gulf of Oman, 
same registration number and jar, BMNH 1937.9.2.550-553, depth 13.5 m, 
triangular dredge, Murray Expedition Stn.53,2.11.33, labelled specimen no. 
3 by present author. They had been identified as Spirobranchus maldivensis 
Pixell according to a label inside the jar; and as Spirobranchus latiscapus 
according to the label on it. 
Description 
Measurements, in the above three specimens as follows. 
Total lengths 7.1-11.5 mm; thoracic widths, 1.5-1.6 mm; 
lengths of operculum and peduncle, 3.0-4.8 mm; lengths of 
operculum alone, 0.3-0.5 mm; and diameters of opercula, 
1.0-1.6 mm. Abdominal lengths 2.6-4.7 mm. Ratios 
of lengths of operculum and peduncle to the lengths of 
abdomen in the three specimens: 0.94: 1.0, 1.02: 1.0 and 
1.15: 1.0. Numbers of radioles: 20 on each side; 21 on 
each side and 27 on the left and 29 on the right. Number 
abdominal segments 40-53. 
T\ibe. Missing in all three specimens. 
Worm. Operculum on left, no rudimentary operculum on 
right. Operculum plus peduncle: about as long as abdomen 
in preserved material (Fig. 53B). Number of stacked 
opercular plates observed, including basal plate: 3 (Fig. 
53B-D) and 2 (Fig. 53A). Peduncle and wings in all three 
specimens transparent; wings unfringed (Fig. 53A-D). 
Largest specimen has 27 radioles plus the operculum on 
left side and 29 radioles on right. Inter-radiolar membranes: 
about l A as long as radioles; unfringed (Fig. 53E). Number 
of thoracic chaetigers: 7; apron present. Maximum number 
of abdominal segments counted: 53. 
Chaetae. Special collar chaetae bayonet shaped, with a 
prominent boss (Fig. 53F,G), sometimes with a constricted 
notch between boss and blade (Fig. 53G). As also seen in 
the latter figure, length of the blade is about Wi times that 
of serrated distal part of the shaft plus boss. Thoracic uncini 
bear 13 or 14 teeth, anterior abdominal uncini 10 or 11, in 
addition to the anterior gouged process. 
Remarks. Opercular plates of all three specimens had an 
epizoic hydrozoan coelenterate belonging to the genus 
Teissiera, Family Teissieridae on them (Fig. 53A), even 
completely covering the gaps between the opercular plates. 
A merely cursory examination could possibly result in the 
present material being identified as belonging to a species 
of Spirobranchus possessing a simple opercular plate, such 
as S. maldivensis, as indeed is evident from the original 
