Pillai: Serpulid polychaetes from the Australian Kimberleys 
165 
unfringed. In contrast, the older tubes of the S. tetraceros 
from the Kimberleys are white, obtusely triangular in cross- 
section, and bear a very low, median longitudinal ridge (Fig. 
44A). Furthermore, its inter-radiolar membranes are fringed 
unlike in the present species. 
Spirobranchus sp. 3 
Fig. 49A-D 
Material examined. BMNH 1959.10.28A, 1 specimen lacking its tube 
and part of its abdomen, Eden, NSW, Australia, collected and presented 
by E.W. and P. Knight-Jones. 
Description 
Measurements. Width of thorax 1.8 mm, length of 
operculum & peduncle 4.0 mm, length of operculum 2.5 
mm, and diameter of operculum 2.0 mm. 
Tube. Missing. 
Worm. Operculum on left side, no rudimentary operculum 
on the right; 20 radioles on each side, some on the left 
appear to have been in a state of regeneration. Operculum 
(Fig. 49B,C) ends distally in a simple, somewhat concave, 
calcareous plate, with a narrow transparent rim, lacks 
processes. Peduncular wings unfringed, although the tip 
of wing of left side is aberrantly bifid (Fig. 49C). Radioles 
arranged in a circle on each side; inter-radiolar membranes 
unfringed (Fig. 49A). Pinnule-free tips of radioles are slightly 
thicker than and about as long as the longest pinnules. Thorax 
with 7 chaetigers; gaps between corresponding pairs of 
thoracic uncinal tori decrease towards posterior end of thorax 
leaving an inverted triangular area between them ventrally 
(Fig. 49A), as in certain other species of the genus. Uncinal 
tori: borne on flap-like extensions of thoracic segments; 
apron present (Fig. 49A). 
Chaetae. Special collar chaetae different from bayonet¬ 
shaped chaetae often associated with Spirobranchus in 
lacking a squarish boss; however, a bend towards the smooth 
side of the shaft indicates transition from the serrated part 
of the chaetal shaft ends to the chaetal blade (Fig. 49D); 
serrations along blade continue to a short distance from its 
tip (Fig. 49D). Thoracic uncini saw-shaped; bear a row of 
about 10-11 teeth and an anterior gouged process; anterior 
and posterior abdominal uncini similar and bear about 9 
teeth. Abdominal chaetae possess long shafts projecting 
beyond abdominal wall; one side of distal end drawn out 
into a tapered process. 
Remarks. Although Spirobranchus sp. 2 is superficially 
similar to S. maldivensis Pixell, 1913, and Spirobranchus 
kraussii Baird, 1861 (= Pomatoleios crosslandi Pixell, 1913) 
in possessing a circular opercular plate lacking opercular 
processes, they differ amongst themselves as follows. The 
opercular plate of S. maldivensis (Fig. 52E), bears concentric 
rings of increasing diameter from the centre outwards, which 
are absent in S. sp. 3 (Fig. 49B) and S. kraussii (Fig. 49E). 
The opercular rim is conspicuous and translucent in S. sp. 
2 (Fig. 52B), thick and non-translucent in S. kraussii, it is 
inconspicuous in S. maldivensis (Fig. 52C,D). The special 
collar chaetae of S. sp. 3 lack a squarish boss (Fig. 49D), 
whereas those of S. maldivensis possess a squarish boss (Fig. 
52G), although not as prominent as in certain other species 
of Spirobranchus, e.g., S. arabicus n.sp. (Fig. 48E,F). While 
special collar chaetae are absent in the adults of S. kraussii, 
they are sometimes present in juveniles; when present, they 
are almost capillairies (Fig. 49G). The thoracic uncinal tori 
in S. sp. 3 are borne on raised flaps (Fig. 49A), unlike in S. 
maldivensis (Fig. 52C,D,F) and S. kraussii (Fig. 49E,F). 
Unfortunately, the tube of the single specimen of S. sp. 
3 is missing; this needs further investigation during future 
studies. Meanwhile, it is worth noting the tube and form in 
the type specimens and additional material of S. maldivensis 
described in this account (Fig. 52B). 
Spirobranchus elatensis n.sp. 
Fig. 50A-F 
Type material. Holotype, BMNH 1995.1659, with its tube, Akaba, Gulf of 
Elat, found growing on a sponge, coll, by U.N. Safriel in 1958, determined 
as Spirobranchus tetraceros (Schmarda) by M.N. Ben-Eliahu. 
Description 
Measurements. Maximum height of tube, including median 
longitudinal ridge, 4.5 mm; 3.5 mm excluding the latter; 
maximum width of tube 4.7 mm. Worm with posterior part 
of its abdomen broken off; posterior ends of two worms 
present in vial. Fength of operculum and peduncle 4.7 mm, 
length of operculum 2.2 mm, diameter of opercular plate 
2.5 mm. Radioles number 19 plus operculum on the left, 
and 19 on the right. 
Tlibe. White, wide anteriorly and narrows abruptly towards 
posterior end (Fig. 50A,B); trapezoidal in cross-sectional 
outline, has a high, wavy, MFR (Fig. 50B), which is thick 
when viewed from above (Fig. 50A), projects conspicuously 
over aperture (Fig. 50A,B). Although apparently nearly flat 
on either side of MFR, actually gently sloping laterally (Fig. 
50B); along on each side of the lateral edge of this almost 
flattened area, is an FFR. Smooth faint transversely arranged 
grooves and ridges present between median and lateral 
longitudinal ridge of each side (Fig. 50A,B). Fongitudinal 
rows of foramina: absent. 
Worm. Operculum on left side, rudimentary operculum 
absent; opercular shape conical; its apex curved dorsally 
and bears vestiges of three opercular horns (Fig. 50C,D); 
latter dichotomously branched and ending in a few short 
transparent spines. Granular deposits of calcareous material 
present along sides of operculum are (Fig. 50C). Peduncular 
wings fringed (Fig. 50D). Branchial radioles arranged in a 
circle on each side; their pinnule-free tips conspicuous and 
about 2Vi times as long as the pinnules. Thorax consists of 
7 chaetigers. 
Chaetae. Special collar chaetae characterized with follow¬ 
ing: boss square and papillate (Fig. 50E,F). Serrations 
present all around distal part of the chaetal shaft (i.e., 
dorsally, laterally and ventrally), unlike in the other species 
of Spirobranchus dealt with in this account, where they 
are present only along the side of the shaft opposite to 
that of the blade and partly along sides of the latter. Ratio 
of length of blade to that of the serrated part of chaetal 
