Figure 4. (a) Dorsal/ventral sides illustrated on examples of (left to right, respectively) Serpulidae (Spirobranchus tetraceros), Sabellidae (Bispira manicata) and Spionidae (Polydora haswelli, stained with methyl green). (b) Arrows indicating paired dorsal radiolar appendages, fused to dorsal lips, in (left to right, respectively) Sabella spallanzanii, Bispira porifera and Bispira manicata. (c) Falcate spines in notochaetae on chaetiger 5 of Polydora uncinata. (d) Anterior regions of Branchiomma bairdi (dorsal view) and Laonome calida (ventral view, stained with methylene blue); arrows indicate faecal grooves. (e) Faecal groove inversion in Branchiomma bairdi: faecal groove runs ventrally in abdomen and dorsally in thorax. (f) SEM image of flat trumpet-shaped abdominal chaetae in Serpula columbiana. (g) Arrows indicate opercula funnels in Hydroides malleolaspinus and Hydroides tuberculatus. (h) Arrow indicates glandular girdle on chaetiger 2 of Euchone variabilis, stained with methylene blue. (i) Arrows indicate handles of acicular thoracic uncini in Euchone limnicola (left) and avicular thoracic uncini in Bispira manicata (right, stained with methyl green). All scales in mm.