120 
Records of the Australian Museum (2009) Vol. 61 
Hydroides minax (Grube, 1878) 
Figs 15A-G, 16A-F 
Serpula minax Grube, 1878: 269, table XV, fig. 5. 
Hydroides minax. —Pillai (1969: 8, fig. 3A-E), Imajima 
(1976: 129, fig. 5), Imajima (1982:42), Imajima & ten 
Hove (1984: 48), Imajima & ten Hove (1986: 3). 
Hydroides monoceros. —Straughan (1967: 221, fig. 6n), Pillai 
(1971: 110, fig. 7D). 
Material examined. Kimberleys, Western Australia; 1 specimen, AM 
W21445, reef north-west of Buffon Island, 14°55'S 124°41'E, 20 m, 23 Jul. 
1988, st 85; 1 specimen AM W20295, south side of Long Reef, 14°01'S 
125°44'E, 20 m, 18 Jul. 1988, st 60; 1 specimen, AM W202936, Bemouli 
Island, 12 Jul. 1988, st 30; all coll, by P.A. Hutchings. 
Additional material examined. BMNH 1924.6.13.132, from the Pearl 
Banks, Sri Lanka, identified by Pillai (1960) as Hydroides minax; BMNH 
1961.8.156, from Zanzibar, determined by C. Crossland as H. monoceros; 
BMNH 1970.828, a specimen identified as H. monoceros by J.H. Day. 
BMNH 1992.320, a juvenile specimen from Matio Is., coll, by P. Gibbs 
during the Royal Society 1965 Expedition to the Solomon Islands and 
determined by H. Zibrowius as H. minax. BMNH 1937.6.6.10, specimens 
from Doom Islands, Sorong, West Irian, Indonesia, coll, by Pillai in 1970, 
determined by ten Hove as H. minax. BMNH, a collection from Akaba, Red 
Sea, by K. Reich in 1936; determined by ten Hove as H. minax. 
Description 
Measurements. From a complete specimen in Kimberleys 
collection AM W21445: maximum width of tube of 4.7 
mm; total length of worm 24.0 mm, its thorax 2.0 mm wide; 
length of operculum and peduncle 8.0 mm, operculum 
alone 4.6 mm. Operculum occurs on right side, rudimentary 
operculum on left; 21 radioles on left side, 18 on right. 
Length of abdomen: 13.3 mm, 122 abdominal segments, with 
capillaries starting from segment 111. Although specimen 
from AM W202951 is incomplete posteriorly, it has two 
well-developed opercula; thorax 1.2 mm wide; lengths of 
two opercula and peduncles, 4.0 mm & 3.5 mm; lengths of 
opercula only, 1.7 mm & 1.9 mm; numbers of coronal spines: 
main spine + 5, and main spine + 6; lengths of main spines 
0.7 mm & 1.0 mm; numbers of infundibular lobes, 18 & 20; 
numbers of radioles, 11 + operculum, and 12 + operculum. 
Tube. White; partially covered over by coral. Although 
surface is irregular due to presence of irregularly shaped 
transverse ridges, two longitudinal ridges can be recognized 
anteriorly, which gives it a trapezoidal cross-sectional 
appearance. That of specimen in AM W21445 has 2 
irregularly developed dorsolateral longitudinal ridges 
anteriorly (Fig. 15A), smooth transverse growth markings, 
a dark-brown pigment overlay in places, and about three 
thickened transverse ridges or peristomes anteriorly, not as 
well developed as in certain other species of Serpula. 
Worm. Operculum blackish in larger specimen AM W21445, 
translucent white with faintly yellowish spines in the second. 
Number of coronal processes 7 in former (Fig. 15D), and 
6 and 7 in the two opercula of second, AM W202951 (Fig. 
16C); all devoid of basal processes. Most dorsal coronal 
process stout, elongated, and terminates in three strong 
sharply pointed hooks, one curved ventromedially and the 
other two curved posterolaterally (Figs 15B-E, 16C); rest 
simple, outwardly curved spines. First specimen has the 
higher number of infundibular lobes, 24. They are simple 
and end distally in a swelling (Figs 15B-E, 16C) which 
may be somewhat T-shaped (Figs 15B, 16C). Maximum 
number of radioles per side in the two specimens is 21; their 
pinnule-free tips short, slender; only slightly thicker than the 
pinnules. A blackish cluster prostomial ocelli present on each 
side, anterior to the second thoracic chaetiger (Fig. 15B,C). 
Abdomen deeply folded along mid-ventral line and its cuticle 
appears to be transversely sloughed off as spicules (Fig. 15C). 
Chaetae. Special collar chaetae bayonet-shaped (Figs 15F,G, 
16D-F), bear 2 conical processes at base of blade. Thoracic 
uncini saw-shaped, with 7 teeth in single row (Fig. 16A); 
anterior abdominal uncini similar, with 4 or 5 teeth (Fig. 
16B); posterior abdominal uncini rasp shaped. Anterior 
abdominal uncinal tori are long, and corresponding pairs 
almost meet or meet along mid-dorsal line (Fig. 15B). 
Anterior abdominal segments bear about 13 chaetae with 
flattened trumped shaped ends. 
Remarks. Pixell (1913), Fauvel (1953) and Straughan 
(1967a,b) distinguish between H. minax (Grube, 1878) and 
H. monoceros Gravier, 1908, on the basis that the corona 
of the latter arises asymmetrically from the infundibulum 
in the former but symmetrically in the latter. Pillai (1971) 
mentioned the difficulty of distinguishing between them, 
and the need for further studies to specify the differences. 
Hartman (1959) believed that they may be synonymous. 
Imajima (1976, 1982) and Imajima & ten Hove (1984, 
1986) considered them synonymous, as also supported in 
the present study. Variations in their coronal spines range 
from those occurring in juvenile specimens of H. minax 
to those in older specimens of H. monoceros. They are 
translucent, somewhat greenish-yellow in colour, and 
the most dorsal coronal spine is very short in juveniles, 
whereas in older specimens they are brownish and the most 
dorsal spine is comparatively very long. The specimen 
with the longest modified coronal spine examined in the 
study is in Crossland’s collection from Zanzibar. Some of 
its measurements are as follows: maximum tube diameter 
3.1 mm; length of operculum and peduncle 6.0 mm; length 
of operculum including long stiff constriction below the 
infundibulum and the peduncle 4.2 mm, and length of most 
dorsal spine 3.0 mm. The tips of infundibular spines may be 
more or less swollen, irrespective of the age and size of the 
worm. Sloughing off spicules of ventrally along the abdomen 
does not appear to occur to the same extent as in Hydroides 
spiculitubus n.sp., described below. 
Hydroides pseudexaltatus n.sp. 
Fig. 17A-K 
Material examined. Kimberleys, Western Australia: holotype: AM 
W202930, island off North East Heywood Island, 15°05'S 124°25'E, rocks 
& mud, low tide, coll. RA. Hutchings, 10 Jul. 1988, st 11. 
Description 
Measurements. Total length of worm 14.2 mm; width of 
thorax 1.1 mm; length of operculum and peduncle 3.6 mm; 
of operculum only 1.6 mm; its diameter 1.0 mm. Fength 
of abdomen 8.1 mm; number of segments 101; capillaries 
commence from segment 86. 
