Pillai: Serpulid polychaetes from the Australian Kimberleys 
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Figure 47. A-C, Spirobranchus sp. 1: two juveniles separated from AM W21432: (A) dorsal view of one of the 
specimens; ( B ) dorsal view of first specimen; (C) ventral view of second specimen. D-F, Spirobranchus acuiconus 
Pillai, 1960, from holotype BMNH 1959.4.14.4: ( D ) tube; (E, F) two views of operculum. 
Chaetae. Special collar chaetae bayonet-shaped; a 
conspicuous squarish boss present; area of shaft preceding 
the boss as well as the boss serrated; an unserrated notch 
absent between the latter and blade (Figs 45C,D, 46F,G), 
the latter two from a juvenile specimen. Thoracic and 
abdominal uncini saw-shaped, with a single row of teeth; 
ending anteriorly in a gouged process. Thoracic uncini bear 
about 10-12 teeth (Figs 45E,F, 46H), latter in a juvenile 
specimen; anterior abdominal uncini bear about 8 or 9 teeth 
(Fig. 46J); may increase to about 13 in posterior segments 
(Fig. 46K). Abdominal neurochaetae possess long shafts 
throughout the entire length of the abdomen (Fig. 45B); their 
flattened trumpet-shaped distal ends asymmetrical, with one 
side drawn into a tapering process (Fig. 461). 
Remarks. From the distribution provided by ten Hove 
(1970a), it appears that a single “tetraceros- type species”, 
S. tetraceros, occurs from the Caribbean region to the Indo- 
Pacific, which would also make it a very ancient species. 
According to ten Hove (1970: figs 7,8), there is overlap in the 
opercular structure between samples from Curasao (Spaanse 
Baai) and those from the Indo-West Pacific. 
However, Spirobranchus tetraceros was originally 
described from New South Wales as Pomatoceros tetraceros 
by Schmarda, 1861. As stated by Smith (1985, unpublished 
thesis) and ten Hove (1994), collections of Spirobranchus 
