PLATE XLll— Continued. 



Fig. 30. Spirorbis cancellatus (Fabricius), p. 248. Bottom view of a calcareous 

 plate. 



31. Nearly front view of same. 



32. Operculum showing calcareous plate becoming detached. 



33. Back view of fig. 31. 



34. Opposite view of fig. 32. 



All figures by the author, X 43* 



(343) 



