Pillai: Serpulid polychaetes from the Australian Kimberleys 
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Figure 20. A-G, Hydroides spiculitubus n.sp.: from holotype AM W21443. (A) dorsolateral view of worm with two 
opercula showing spicules sloughed off from ventral side of abdomen, dorsolateral anterior abdominal tori and pair 
of eyespots on anal segment; ( B ) dorsolateral view of second specimen with a single operculum, showing dorsolateral 
arrangement of anterior abdominal tori and pair of anal eyespots; (Q operculum; ( D,G ) enlarged view of posterior 
ends of two worms showing the eye-spots on anal segment; ( E,F ) bayonet-shaped special collar chaetae. 
fig. 12A,B). The basal process of each coronal spine in H. 
spiculitubus is slender, and acutely hooked towards the centre 
of the corona (Fig. 21D,E), whereas it is is obtusely triangular 
and blunt in H. tambalagamensis (Pillai, 1961: fig. 12B). 
A further, very important difference between the two 
species is with regard to pinnule-free tips of radioles. 
In H. spiculitubus they are soft and similar in texture to 
that of pinnules (Fig. 20A,B), as also in almost all other 
serpulimorphs. However, as confirmed after re-examination 
of the type specimen during this study, each radiole in H. 
tambalagamensis , terminates in a stiff, chitinous colourless, 
inwardly curved, pointed hook (vide Pillai, 1961: 38, fig. 12C). 
Anal eyespots are present in H. spiculitubus , but were 
not observed in the Southwest Japan material by Imajima 
(1976), material from China by Chen & Wu (2000), and H. 
tambalagamensis by Pillai (1961). 
As described earlier, there are two important differences 
between the two species with regard to the tube. The first is 
the characteristic detachable inner tube of H. spiculitubus, 
composed of more or less transversely adposed chitinous 
spicules sloughed off from the ventral side of its abdomen 
(Fig. 19D), the function of which is obscure. In contrast, 
H. tambalagamensis has no such inner tube consisting of 
chitinous spicules as originally described by Pillai (1961). 
Imajima (1976) and Chen & Wu (2000) do not mention it in 
their descriptions of “77. tambalagamensis”. 
The second difference concerns the pair of longitudinal 
ridges along their tubes. In the material described as “77. 
tambalagamensis ” from Southwest Japan by Imajima (1976: 
123, fig. 2a—j) they are dorsolateral, separated by a relatively 
wide and shallow gap, which may also vary somewhat in 
width in different parts of the tube. Its granular overlay is 
concentrated along the longitudinal ridges and lateral edges 
of the tube. In 77. tambalagamensis Pillai, 1961, on the other 
