- the opening at the lower end of the alimentary canal, through which the solid refuse of digestion is excreted.
- Anus posterior, median; anterior tentacles, atrophied; foot broad.
- Anus nearly always terminal, rarely dorsal, at a little distance from end of body.
- Anus orange-coloured, and furnished with a bristle for oviposition.
- Anus usually in the upper or oral half of the theca, and never aboral.
- Anus in posterior interradius, on oral surface, closed by valvular pyramid.