Lineolariidae
Diagnostic description:
Small thecate hydroids with stolonal colonies growing on an underlying sheet of perisarc. Hydrotheca sessile, deep, tubular to saccate, with an upturned, untoothed or lobate margin; operculum a simple flap or conical, of converging segments demarcated from the margin. Hydranth slender and extensile, with a ring of filiform tentacles. Nematophores present or absent. Gonotheca sessile, gonophore a fixed sporosac.