(From Cutler, 1994)
Trunk cylindrical longer than 50 mm in adults, covered by swollen rectangular “minipillows”.
Introvert shorter than the trunk (5-30%).
Hooks absent but introvert covered with irregularly arranged triangular papillae.
Coelomic extensions in the body wall in the form of canals between longitudinal muscle bands.
Longitudinal muscles and circular muscles divided in distinct bands (LMBs, and CMBs respectively).
Tentacles arranged around the mouth, sometimes with an intertentacular membrane.
Two pairs of retractor muscles.
Two smooth contractile vessels, no villi.
Gut with postesophageal loop, and attached to the trunk wall by connective tissue strands.
Rectal caecum present.
Spindle muscle not attached to the trunk wall posteriorly.
A pair of nephridia.