Pillai: Serpulid polychaetes from the Australian Kimberleys 
125 
Dew (1959) states that the crown consists of nine “stout 
inwardly-pointing spines, largest and stoutest of which curve 
over remaining eight, forming a cage.” Dew’s (1959) fig. 7B 
shows a single enlarged spine. It is evident that one or more 
enlarged coronal spines may be curved over the centre of 
the crown. While a shoulder can be faintly recognized in 
the four larger spines, they are strongly developed in the 
remaining coronal spines, being tooth-like as described 
by Dew (1959) and Straughan (1967a). Firstly, its main 
process is a strong curved spine {vide Dew, 1959: fig. 7B). 
Secondly, as described by Dew, “remaining spines, except 
pair flanking large spine, have a blunt, tooth-like projection 
on shoulder of curve”. Straughan’s (1967a) description is 
similar. In contrast, both H. brachyacanthus Rioja, 1941 and 
H. simplidentatus a single enlarged process curves over the 
centre of the crown. Further studies are required to determine 
whether Straughan’s Eastern Australian material belongs to 
a species different from H. brachyacanthus Rioja. 
Etymology. The specific name simplidentatus refers to 
the simple unmodified spines at the base of the enlarged 
coronal spine. 
Hydroides spiculitubus n.sp. 
Figs 19A-E, 20A-G, 21A-I 
Hydroides tambalagamensis Pillai, 1961.—Straughan 
(1967b: 33, fig. 3g), Imajima (1976: fig. a-j) Imajima 
(1979:167), Sun & Yang (2000: 128, fig. 6K-S), Imajima 
& ten Hove (1984: 49), Imajima & ten Hove (1986: 4). 
Type material. Kimberleys, Western Australia. Type specimens: holotype, 
AM W21443, Long Reef, 13°58'S 125°38'E, 25 m, 17 Jul. 1988, st 58. 
Paratypes (2), first: AM W21468, south-west corner of Lucas Island, 
15°13’S 124°31'E, 30 m, st 101. Second paratype: AM W21390, east side 
of Fenelon Island, 14°07'S 125°43'E, 6 m; all coll, by P.A. Hutchings, 18 
Jul. 1988, st 64. 
Description 
Measurements. Appears to be very small species. Maximum 
tube diameter: 2.1 mm ; total lengths: 9.7 mm, 10.3 mm and 
14.8 mm, thoracic widths 1.0 mm, 1.0 mm and 0.7 mm. 
Specimen 1 has a single operculum, while 2 & 3 have two 
opercula each. Total lengths of their opercula and peduncles 
(the longer when two are present): 2.4 mm, 3.3 mm and 3.3 
mm; their abdominal lengths and respective numbers of 
abdominal segments: 5.3 mm and 61 segments, 6.0 mm and 
66 segments, and 8.6 mm and 86 segments. Commencement 
of abdominal capillaries in the three specimens, as follows: 
on segments 51, 55 and 69, respectively. Numbers of 
branchial radiole, respectively, as follows: 9 plus operculum 
on right, 8 plus no rudimentary operculum on left; 9 plus 
operculum on left and 9 plus operculum on right; and 10 plus 
operculum on left and 9 plus operculum on right. 
Tube. White, with two dorsolateral longitudinal ridges 
separated by a moderately wide longitudinal gap which, 
together with the flange on either side, gives it a trapezoidal 
cross-sectional appearance (Fig. 19A-C); conspicuous 
transverse ridges and grooves present (Fig. 19A-C); a 
granular, semi-translucent, overlay present, especially along 
longitudinal and transverse ridges and flanks (Fig. 19A-D). 
An unexpected character, hitherto unreported in any 
other Hydroides species, is the presence, in all three 
specimens, of a detachable inner tube (Fig. 19D). Under 
high examination, consists of transversely arranged, closely 
adposed, spicules (Fig. 19D,E) sloughed off from the 
ventral abdominal wall (Fig. 20A). 
Worm. A brown pigment patch may be present in 
constriction between operculum and peduncle (Fig. 20C); 
ventral side of thorax and edges of thoracic membrane brown; 
a brown pigment band present anterior to each thoracic 
uncinal torus (Fig. 20A). Abdomen: a narrow pigment band 
present anterior to each torus, ending ventrally in a brown 
patch; a similar pigment band present across ventral side of 
each segment joining corresponding ventral patches of both 
sides. One or two opercula may be present. Tips of coronal 
spines and their lateral spines, black. One specimen has a 
single operculum (Fig. 20B), the other, two well-developed 
opercula each (Fig. 20A). Three out of the 5 opercula among 
them, bear 7 coronal spines, the remaining two bear 6. All 
spines are similar (homospinous) and tapering; initially 
directed anteriorly and inclined towards the centre of the 
crown rather than outwards, then curved outwards before 
ending in curved pointed tips (Figs 20A-C, 21A-E). 
Focated a little less than halfway along each spine and 
arising from it, externally, is a pair of short outwardly 
directed spines (Figs 20B,C, 21A-E). A medial spine is, 
present arising a little distal to the pair of lateral spines, as 
well as a basal process, both sharply hooked towards the 
base of the crown (Fig. 21D,E). Infundibulum: out of the five 
opercula amongst the three specimens one has 31 marginal 
processes, two 28, one 27, and one 26. Infundibular spines: 
transparent, their tips light brown; each marginal process 
has a sub-terminal knee-like bend towards centre of crown, 
beyond which it tapers to a simple pointed outwardly curved 
process (Fig. 21C). An aberrant condition occurs in one 
specimen, in which a single marginal infundibular process 
in one of its opercula is forked. 
Maximum number of branchial radioles counted per side: 
9 in all three specimens. However, specimen separated from 
AM W21390, has 11 radioles per side; their pinnule-free tips 
slender, and increase in length from ventral to dorsal radioles; 
about one-sixth of total length of radiole. 
A light-brown cluster of prostomial ocelli present on each 
side, just anterior to the first pair of uncinal tori. Thoracic 
glands: absent. Anal segment bears a pair of brown to 
blackish clusters of ocelli (Fig. 20A,B,D,G). 
Chaetae. Bayonet-shaped special collar chaetae (Figs 20E,F, 
21F,G) possess two broad conical teeth at the base of the 
serrated blade. The unserrated notch is short. Thoracic and 
anterior abdominal uncini: saw-shaped, with 6 and 5 teeth, 
respectively (Fig. 21H,I); posterior abdominal uncini rasp¬ 
shaped. The anterior abdominal tori are dorsolateral, with a 
moderately wide gap separating them (Fig. 20B). 
Remarks. The new species H. spiculitubus from the Kim¬ 
berleys is only superficially similar to H. tambalagamensis 
from Sri Fanka with regard to the operculum. This has 
apparently led to the latter being reported from Southwest 
Japan by Imajima (1976: fig. 2a), and by Chen & Wu (2000: 
fig. 6K,F) from the waters off China. 
Both species are similar in that their coronal spines are 
homospinous, and each bears a pair of short pointed spines 
located about halfway along its length, a short, inwardly 
