EXPLANATION OF THE PLATES. 357 



dorsal brush of a segment from near the middle of the body. 

 8. Another bristle from the same. 9. A bristle from the ven- 

 tral brush, 10. One of the small bristles associated with the 

 preceding : — magnified. 



Figs. 11-18. Trnvisia Forbesii. 11. Nat. size. 12. Animal mag- 

 nified. 13. Cephalic segments, 14. Side view of a segment 

 from near the middle. 15. View of a caudal segment on the 

 dorsal aspect. 16. The same on the ventral aspect. 17. Anal 

 segments, 18, A few bristles : — magnified, 



Plate XX. 

 Opercula of different species of Serpula. 



Fig. 1. Operculum oi Serpula conica (see p, 347). 2, Operculum of 

 Serpula armata (p. 347), 3. Operculum of Serpida Dysteri 

 (p. 347). 4. Operculum oi Serpula Berl-eleii (p. 346), 5, Oper- 

 culum of Serpula intricata (p, 346). 6, 7. Operculum of Ser- 

 pula reversa, two views (p, 346). 



