PLATE LV. 
Fig. 1 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
Pig. 6. 
Fig. 7. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Anterior region of Serpula narconensis, viewed from the right side, 
Tubes and anterior end of Serpula narconensis, var. magellanica. 
The rounded bodies attached to the tubes are Ascidians, 
Operculum of Pomatocerus strigiceps, showing three tiers, 
Anterior region of another example of the same species, with 
only a single plate in the operculum. 
Portion of the tube of Placostegus ornatus, 
Branchiae and operculum of the foregoing. 
Portion of the tube of Placostegus henthalianus, . 
Fragment of the tube with branchiae and operculum of Placostegus 
morchii, . . . . . . 
Anterior region of the tube with the operculum and the tips 
of branchiae of Placostegus assimilis, 
Operculum of Spirohranchus occidentalis, 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
Enlarged. 
