This species can be confused with S. nudus, however S. mundanus has a pair of small protractor muscles of the introvert and free nephridia that separate it from S. nudus.
This species superficially resembles S. nudus, but is distguished by the presence of a pair of protractor muscles, and free nephridia.
(Edmonds, 1980; Cutler and Cutler, 1985; Cutler, 1994)
Introvert shorter than the trunk, 10-20 mm longby 4-7 mm wide, bearing scale-like papillae posteriorly directed.
Trunk is cylindrical measuring 130-270 mm of length by 7-12 mm wide. The surface of the trunk is divided into a large number of small rectangles by the intersection of the longitudinal and circular muscles.
27-31 longitudinal muscle bands (LMBs).
A pair of free nephridia.
Brain bilobed with anterior tufted dititate processes.
A pair of short dorsal protractor muscles (less than 2% of the trunk length) arises from the trunk wall of the anterior part of the trunk, and attaches to the introvert near the brain.
A pair of retractor muscles arises at the same level, the ventral pair originates in LMBs 2-4, 1-3, 1-4, and the dorsal in 7-10, 7-11, 8-11.
Spindle muscle originates from the anterior ventral surface of rectum.
Specimens up to 270 mm in trunk length.
Most records are from the South Pacific with one record from the eastern Pacific in Chile (Cutler, 1994).
Probably collected in shallow water (Cutler, 1994).