Appendages of body re „ duced to branchiae, present only in four species, and - - to the ventral copulatory 32 appendages of Alma and Criodrilus.
The ganglia are crowded at the posterior end of the body as in leeches, and there is much tendency to the obliteration of the coelom as in that group. Pterodrilus and Cirrodrilus bear a few, or circles of, external processes which may be branchiae; Bdellodrilus and Astacobdella have none.
The appendages of the body are reduced to branchiae, present in certain forms. A clitellum is present.
Further, the Pleurotomariidae have been discovered to possess two branchiae.
Helcion, circlet of branchiae interrupted anteriorly, British.