Hymedesmia jecusculum is a species of demosponge in the family Hymedesmiidae.
This species was described from a cave on the coast of Harris in the Outer Hebrides, Scotland, United Kingdom where it was collected at low water spring tides by Captain F.W.L Thomas of the Hydrological Survey.
This sponge has acanthostyles of two size classes, 360-430 üm and 120-140 üm in length. The skeleton spicules are slightly fusiform tornotes with one end pointed and the other slightly rounded, 270-350 üm in length. The chelae are curved isochelae with the alae equal to the gap between them, 20-26 üm in length.