Description: Thin sheet or cushion, developing into branching-repent form with anastomosing branches, 3 - 4mm diameter. Pale yellow, purple only when preserved. The colour change on preservation in alcohol to brown is distinctive, paper labels are stained brown. Moderately soft, branches have no axial skeletal structure and apparently only develop fully in fairly sheltered conditions. Friable and not easy to section. Oscules "small, scattered", not obvious.

Habitat: On shells such as Modiolus modiolus, Chlamys varia, and Aequipecten opercularis; on rocks, in localities sheltered from wave action, with no or slight tidal action. "On hydroids, other sponges, coralline algae, nullipores, fucoids, etc."

Distribution: "Norway; British Isles; France; Mediterranean." Recent voucher specimens from Strangford Lough (the original type specimen was collected from Strangford Lough by Hyndman). Also Mulroy Bay; Lough Hyne; Rathlin Is.; Kilkieran Bay; Skomer; Loch Sunart, Loch Fyne. Common.

Distribution Map from NBN: Iophon hyndmani at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Iophon hyndmani at iNaturalist World Species Observations database.