46 



T.G. PILLAI AND HA. TEN HOVE 



d.cx.w. 

 dr. 



Fig. 1 Terminology. A, Tube: d.cx.w., dorsal convex wall; d.r., dorsal ridge; v.cv.w., ventral concave wall; v.r., ventral ridge. B, Radioles 

 of both sides and operculum: o.p., opercular peduncle; p., pinnules; pf.t., pinnule-free tip; r., radius; rl., radiole; r.l.s., radioles of left 

 side; r.o., rudimentary operculum; r.r.s., radioles of right side; t.r.l. triangular radial lobe; z.o., zygomorph operculum. C-G, Opercula: 

 en., constriction between operculum and peduncle; i.r.g., inter-radial groove; ut.c, unthickened cuticle, bs.o., bell-shaped operculum; 

 r.r.l., rounded radial lobe; t.t.c., thickened transparent cuticle. 



mutually bonded aggregations of a few to numerous individu- 

 als. 



An operculum similar to that in Serpula, which is a 

 modification of the second most dorsal radiole, is often 

 present on one side with, correspondingly, a rudimentary 

 operculum on the other. There may only be a rudimentary 

 operculum on each side in certain species, while they may be 

 present in juveniles and completely lost in older specimens in 

 others. The shape of the fully developed operculum is charac- 

 teristic for a particular species; it may be funnel-shaped, 

 bell-shaped, zygomorphic or spherical. Its distal end may be 

 concave or convex and usually bears radii which end as 

 triangular or rounded lobes at the rim; but radii may also be 

 lacking in some species. Its cuticle may be unthickened or 

 thickened and transparent. 



The number of branchial radioles is usually small, rarely up 

 to 14 pairs. Palps absent. A pair of prostomial ocellar clusters 

 is usually present. The number of thoracic chaetal tufts may 

 exceed the seven pairs commonly occurring in many genera 

 of Serpulidae, including Serpula, and those of the two sides 

 are more frequently asymmetrical than symmetrical. Up to 14 

 have been counted on each side. Histological work is needed 

 to ascertain the real extent of the segments, and their relation 

 to numbers of chaetal tufts and uncinal rows, etc. The term 

 'chaetiger' is, therefore, used here in the literal meaning of 

 'hair bearer' and not as a synonym of segment. The thoracic 



membranes end anterior to the last thoracic chaetigers, also 

 more frequently asymmetrically than symmetrically. Unlike 

 in most species of Serpula sensu stricto, therefore, a post- 

 thoracic ventral flap (apron) is absent. 



Collar fascicles bear chaetae of two kinds: bayonet 

 chaetae and limbate chaetae, the blades of both of which 

 are usually finely serrated. In the former, there are a few to 

 several comparatively large teeth, located at the distal end 

 of the shaft, separated from the bayonet-like blade by an 

 unserrated area (unserrated notch). The range in the 

 number of such teeth and the length of the unserrated 

 notch varies in the different species. Limbate chaetae bear 

 simple, more or less curved, blades. Thoracic and anterior 

 abdominal uncini may bear teeth in a single row (saw- 

 shaped), or are partly (saw- to rasp-shaped) or completely 

 rasp-shaped. Abdominal chaetae bear distally flat trumpet- 

 shaped ends, and are replaced by capillaries in the poste- 

 rior segments. The distal ends of the abdominal chaetae of 

 Serpula have been described as 'trumpet-shaped' in ser- 

 pulid literature. We have discussed the inappropriateness 

 of the comparison, as demonstrated by the scanning elec- 

 tron micrographs and drawings of these chaetae presented 

 in this paper, and our attention has also been drawn to this 

 by Zibrowius (pers. comm.). In order not to create confu- 

 sion, it was decided to retain 'flat trumpet-shaped', for the 

 present. 



