Phascolion (Isomya) cf. hedraeum Selenka & de Man

Phascolion hedraeum Selenka & de Man in Selenka et al., 1883: 49 –50.

Type locality: Rio de Janeiro, 7 m.

Remarks: The six 2–12 mm worms had been living in gastropod shells. The holdfast papillae are circular, with only their anterior margins showing pale hardened protein, which may be dark in a few cases. Scattered pale hooks can be seen. The two retractor muscles are of almost equal size, but the smaller one may be only 65–70% the diameter of the larger, both having their origins at the same level very close to the posterior end of the trunk. The similarities to P. tuberculosum are significant and in some ways these small specimens did not fit perfectly into either taxon (thus the cf. designation), but most closely resemble P. hedraeum .

Distribution: Southern Atlantic reports give latitudes down to 74° S. Some records are from the southern Pacific, near Australia, and also off Japan. They live at shelf and slope depths, rarely over 800 m, in gastropod or scaphopod shells. The present collection suggests the possible existence of a low­density bathyal population in this part of the southern hemisphere.