118 
Records of the Australian Museum (2009) Vol. 61 
Hydroides kimberleyensis n.sp. 
Figs 14A-Q 
Type material. Kimberleys, Western Australia, holotype: AM W21391, 
east side of Fenelon Island, 14°07'S 125°43'E, 6 m, 18 Jul. 1988, st 64. 
Paratype, AM W202963, reef north-west of Buffon Island, 14°55'S 
124°48'E, 20 m, 23 Jul. 1988, st 85; both coll, by P.A. Hutchings. 
Description 
Measurements. Apparently a very small species; maximum 
external tube diameter: 1.2 mm in holotype, 1.0 mm in 
paratype. Total length of longer of the two worms is 10.0 mm, 
the other 9.1 mm. However, latter sexually mature, since ova 
being present in posterior part of abdomen. Thoracic width: 
only 0.5 mm in both. Length of operculum and peduncle 
2.5 mm in first specimen, 1.7 mm in the second; length of 
abdomen, 5.1 mm long in first specimen, 7.3 mm in second. 
Number of abdominal segments: 66 in first, 71 in second; 
capillaries starting from 63rd segment in both. 
Tlibe. Light caramel coloured in holotype, white in paratype; 
lined internally by chitin-like material, light brown in the 
former, more conspicuous and darker brown in the latter. It 
has a characteristically wide, apparently flattened dorsal area 
with a longitudinal ridge on each side, sloping sides, and a 
flange on each side, giving it a trapezoidal cross-sectional 
appearance (Fig. 14Q). Fine transverse ridges traverse the 
gap between the two longitudinal ridges, most of them not 
extending beyond the wide mid-dorsal longitudinal groove 
itself, thus leaving the longitudinal ridges comparatively 
clear. Irregular transverse ridges present along the flanks; a 
granular overlay absent. 
Worm. Posterior part of collar and ventral side of thorax 
brown; a transverse brown band present anterior to each 
thoracic uncinal torus; brownish pigmentation present 
transversely across ventral side of abdominal segments, 
fainter bands dorsally in posterior part of abdomen, latter 
more pronounced in second specimen. Infundibular lobes 
are brown distally, their tips blackish; opercular peduncle 
whitish. 
Operculum on the right side in both specimens; number 
of radioles radioles 8 per side, their pinnule-free tips as long 
as and as thick as pinnules (Fig. 14A,L,Q). Corona of both 
specimens has 5 triangular, brownish, chitinous processes 
each, which arise directly from the infundibulum, i.e., not 
collectively borne on neck-like part arising from it (Fig. 
14A-D,L-P,Q); their blunt tips directed outwards. Diameter 
of coronal base somewhat greater than or equal to that of 
infundibulum, so that, when viewed from anterior end, 
only the pointed tips of the marginal infundibular processes 
may be seen, if at all (Fig. 14D,N). Coronal processes (Fig. 
14A-D,L-P,Q) translucent light brown, their tips and edges 
transparent light brown to honey coloured; each roughly 
triangular in cross-section, thick and ending distally in a 
bluntly pointed transparent tip; also possesses, medially, at 
it base, 4-5 tiny processes (Fig. 14D). Coronal processes 
are all similar in holotype (Fig. 14B,C); in the paratype, the 
translucent part at the tip of one of the coronal spines bears 
a short, sharp, translucent, medial sub-terminal spine (Fig. 
140,P), which appears to represent the fully developed 
condition. 
Infundibular lobes minute, acutely triangular, and end in 
outwardly curved pointed tips (Fig. 14A-C,L-P,Q). They 
number 24 in the holotype, difficult to count in the paratype. 
Two faintly brown clusters, of what appear to be prostomial 
ocelli, present in the first specimen, darker and clearer in 
the second. Thoracic glands: not discernible. Anal segment 
appears to bear a pair of ocellar clusters; they are clearer in 
the second. 
Chaetae. Each collar fascicle bears about 5 bayonet-shaped 
special collar chaetae. Two newly formed ones from within 
the fascicle possess a small accessory tooth between two 
larger conical teeth (Fig. 14E,F); remaining three older, 
their blades and accessory tooth and conical teeth at the base 
of blade worn out (Fig. 14G-I). In newly formed bayonet 
chaetae, the unserrated notch is comparatively short, about 
one-tenth to about one-twelfth of the total length of the 
blade (Fig. 14E,F). Thoracic uncini (Fig. 14J) and anterior 
abdominal uncini (Fig. 14K): saw-shaped, bear 6 and 5 
teeth, respectively; posterior abdominal uncini rasp-shaped. 
Abdominal uncinal tori: 15 or so pairs of anterior abdominal 
tori are dorsolateral, with a wide gap separating the tori of 
the two sides (Fig. 14A). 
Remarks. Hydroides kimberleyensis is somewhat similar 
with regard to its small size and characters of its coronal 
processes to H. xishaensis Chen & Wu, 1978, H. trilobulus 
Chen & Wu, 1978, and H. rhombobulus Chen & Wu, 1980, 
but there are important differences among them. Total lengths 
of their holotypes are, only 4.8 mm for H. xishaensis and 4.0 
mm for H. trilobulus, while it is 9.0 mm for H. rhombobulus 
Chen & Wu, (1980: 250). Total lengths of the two specimens 
of H. kimberleyensis are 10.0 mm and 9.1 mm, respectively. 
In spite of their comparatively minute sizes, the holotype of 
H. xishaensis has a total of 20-24 branchial radioles (10-12 
per side), while that of H. trilobulus has a total of 20-26 
(i.e., 10-13 per side). On the other hand, the holotype of 
H. kimberleyensis has only 16 radioles (8 per side). The 
9.0 mm holotype of H. rhombobulus has 12 radioles (6 per 
side), somewhat similar to H. kimberleyensis in this respect. 
The number of coronal processes in both specimens of H. 
kimberleyensis is 5, but it is 4 in H. rhombobulus. Moreover, 
the colour and form of coronal processes in H. kimberleyensis 
and H. rhombobulus are different. In H. kimberleyensis 
they are brownish, triangular, convex on the outside, with 
transparent edges and tips, and each bears 4-5 tiny basal 
processes (Fig. 14D). In H. rhombobulus, on the hand, the 
coronal spines are rhomboidal in shape and apparently lack 
medial basal processes. In H. kimberleyensis, the diameter of 
the infundibulum and infundibular processes is nearly equal 
to that of the corona, the infundibular lobes slender, and their 
pointed tips pressed closely against the coronal base (Fig. 
14A-D,F-Q,). In H. rhombobulus, on the other hand, the 
diameter of the infundibulum and infundibular processes is 
greater than that of the corona, and its infundibular lobes are 
directed outwards (Chen & Wu, 1980: pi. 1, fig. 1). Minor 
differences also appear to exist in their chaetae. Bayonet 
shaped collar chaetae of H. kimberleyensis typically possess 
two conical processes at the base of the blade, with a smaller 
accessory tooth between them, but in H. rhombobulus they 
have been described and figured as possessing only two 
conical processes. Thoracic and abdominal uncini of H. 
kimberleyensis bear 6 and 5 teeth, respectively, whereas they 
bear 7 and 6, respectively, in H. rhombobulus. 
