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Records of the Australian Museum (2009) Vol. 61 
Figure 58. A-D, Spirobranchus sp. 5. (A) tube on coral; normally overlaid with the coral on which it grows, most of it has been cleared, 
except towards its middle; ( B ) part of a tube viewed from the side attached to the substratum. More or less transversely elongated chambers 
are present on either side of the mid-ventral line; ( C,D ) dorsal views of two portions of a tube: a comparatively wide, nearly horizontal area 
occurs on either side of a smooth MLR, which may be discontinuous in places. Along the lateral border of each horizontal area is a LLR. 
thick, wavy MLR which ends anteriorly as a short pointed 
tooth over the aperture (Fig. 57, A,B). Operculum in the 
larger specimen bears four separate horns, the dorsal pair 
being longer than the ventral pair. Each of the dorsal pair of 
horns is branched only once, one branch being dorsomedial 
and the other dorsolateral (Fig. 57C,D), the former being 
very short compared to the other. The two ventral horns 
are un-branched. Inter-radiolar membranes are unfringed. 
The second specimen is similar, although its two ventral 
opercular horns appear to arise from a common base. 
In the two specimens identified above as S. semperi var. 
acroceros are similar, but for the fact that its four horns, 
which comparatively shorter, arise from a conical opercular 
plate. Its inter-radiolar membranes are also unfringed, and 
