Its hydroid form grows as feathery stems resembling seaweed from a basal stolon. Corymorphidae is a family of hydroid cnidarians. Tubulariidae is a family of hydroid cnidarians. Species of hydroid are sometimes found growing on the mollusc shells occupied by hermit crabs. When colonial, the hydranths or hydroid polyps are either linked by stolons or are branched. Eudendrium speciosum is a marine species of cnidaria, a hydroid (Hydrozoa) in the family Eudendriidae. Eudendrium rugosum is a marine species of cnidaria, a hydroid (Hydrozoa) in the family Eudendriidae. Eudendrium novazealandiae is a marine species of cnidaria, a hydroid (Hydrozoa) in the family Eudendriidae. Eudendrium macquariensis is a marine species of cnidaria, a hydroid (Hydrozoa) in the family Eudendriidae. A hydroid is a type of vascular cell that occurs in certain bryophytes. The hydroid form is usually colonial, with multiple polyps connected by tubelike hydrocauli. Stylaster nobilis, the noble coral, is a branching colonial hydroid in the family Stylasteridae. The hydroid looks superficially like fronds of seaweed. Pycnotheca mirabilis, The feathery hydroid, is a colonial hydroid in the family Kirchenpaueriidae. The hydroid "Hydractinia angusta" has a mutualistic relationship with the scallop.