Pillai: Serpulid polychaetes from the Australian Kimberleys 
179 
Figure 57. A-H, Spirobranchus semperi Morch, 1861; from the Pearl Banks, Sri Lanka, determined by Pillai (1960). (A) tube 
viewed from above; ( B ) lateral view of tube; (C) opercular horns, viewed laterally; (D) an anterodorsal view of operculum; 
(E) bayonet-shaped special collar chaeta; (F) thoracic uncini; (G) anterior abdominal uncini; ( H) abdominal neurochaetae. 
Chaetae. Special collar chaetae of S. semperi bayonet¬ 
shaped (Fig. 57E): blade narrow and tapering, about half 
as wide as the distal part of the shaft, about IV 2 t im es the 
length of serrated distal part of shaft, boss squarish. Thoracic 
uncini saw-shaped (Fig. 57F) and bear about 15 teeth and an 
anterior gouged process. Special collar chaetae of S. semperi 
Morch, 1861, var. acroceros are similar (Pillai, 1960: fig. 
7B), except that the chaetal shaft on the opposite side of the 
boss is more curved. 
Remarks. Spirobranchus semperi can be distinguished 
from S. tetraceros as follows. In S. semperi, tube colour 
is bright pink to pinkish orange on a white background, 
has a more or less circular outline, and a high, prominent 
