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Records of the Australian Museum (2009) Vol. 61 
Figure 24. A-J, Hydroides trihamulatus n.sp. (A,B) anterior and posterior parts of tube of a juvenile specimen; (C) worm, showing operculum, 
operculum, pinnule-free tips of radioles and arrangement of anterior abdominal tori; D-F, from another somewhat older specimen: ( D ) 
anterior end of worm, showing operculum, its well-formed main coronal spine, and remaining coronal spines and infundibular spines 
with simple pointed tips; ( E ) tube with worm in situ\ (F) operculum showing somewhat swollen processes; (G) operculum of still older 
specimen showing well-formed main coronal spine and remaining coronal and infundibular spines with T-shaped tipas. 
and 1 or 2 small accessory teeth between them; unserrated 
notch short, about !4 length of blade. Thoracic uncini: saw¬ 
shaped, with 6-7 teeth in a single row (Fig. 26K); anterior 
abdominal uncini similar, with 4 or 5 teeth (Fig. 26L); 
posterior abdominal uncini rasp-shaped. Anterior abdominal 
uncinal tori of the two sides are separated by a narrow gap 
(Fig. 24C); which is wider in juveniles (Fig. 26D). 
Remarks. The new species, Hydroides trihamulatus is 
apparently similar to H. malleolaspina Straughan (1967: 
222, fig. 7a-f), originally described from Queensland, with 
regard to the T-shaped infundibular and modified coronal 
spines. However, it is different with regard to the modified 
coronal spine. Straughan (1967) describes the latter in H. 
malleolaspina as being hammer-shaped distally and lacking a 
medial process, whereas, in H. trihamulatus, it ends in a bifid 
tip and bears a medial hooked process. Although the medial 
process and both processes at the distal end of the modified 
coronal spine are soft and blunt in juveniles of the present 
species (Fig. 24C-F), they are firm and beak-like in adults 
(Fig. 25A-C). Hydroides rectus Straughan (1967: 225, fig. 
8a-f) differs from both H. malleolaspina and H. trihamulatus 
in that its unmodified coronal spines and infundibular spines 
are not T-shaped but tapered and pointed distally, as described 
and figured by Straughan (1967: 225, fig. 8b-d). Moreover, 
the modified coronal spine of H. rectus is not bifid at its tip as 
in H. trihamulatus, but has a process at its distal end, which 
appears to be at right angles to it and directed towards the 
centre of the crown. 
Imajima & ten Hove (1984: 45-47) discuss H. novae- 
pommeraniae Augener, 1925; H. grubei Pillai, 1971, H. 
malleolaspina Straughan, 1967, H. recta Straughan, 1967, 
and H. ancorispina Pillai, 1971, and conclude by recognizing 
the following three species in the Indo-Pacific region. 
