PLATE XLII. 



Fig. I. Spirorbi's spirillum (Linne) var. hccidus (Montagu), p. 243. Back view 

 of a calcareous plate from an operculum of specimen from Green- 

 land. 



2. Nearly front view of an operculum showing calcareous plate from 



another specimen from Greenland. 



3. Calcareous plate from operculum of a specimen (typical luctdus) from 



Casco Bay. 



4. Operculum of specimen from same locality, showing calcareous plate 



covered with a minute seaweed. 



5. Back view of fig. 3. 



6. Spirorbis vitreus (Fabricius), p. 247. Calcareous plate from operculum 



of specimen from the Banks, Atlantic Ocean. 



7. Top view of same. 



8. Spirorbis violaceus Levinsen, p. 242. Operculum showing calcareous 



plate of specimen from Grand Banks. 



9. Opposite view of same. 



10. Bottom view of calcareous plate from another operculum. 



11. Back view of same. 



12. Front view of same. 



13. spirorbis tubceformis sp. nov., p. 251. Back view of an operculum 



showing calcareous plate of specimen from Long Island Sound. 



14. Front view of same, the plate covered with seaweed. 



15. Spirorbis spirorbis (Linne), p. 236. Back view of an operculum from 



a full-grown specimen from Gloucester, Massachusetts. 



16. Side view of an operculum of a medium sized specimen, showing 



calcareous plate. 



17. Front view of fig. 15 ; the plate covered with minute protozoans. 



18. Back view of an operculum showing operculum plate, of a young 



specimen. 



19. Front view of same. 



20. Spirorbis evolutus sp. nov., p. 251. Front view of an operculum 



showing calcareous plate of specimen from Grand Banks. 



21. Opposite view of same. 



22. Side view of same. 



23. Spirorbis quadrangularis Stimpson, p. 241. Side view of calcareous 



plate of specimen from Greenland. 



24. Front view of calcareous plate, fig. 28. 



25. Back view of same. 



26. Opposite view of fig. 23. 



27. Side view of operculum of a specimen from Greenland collected and 



identified as 6". granulatus by Moore, 1902. 



28. Front view of another operculum from specimen from same locality. 



29. Opposite view of same. 



(342) 



