Filellum serpens
Hydrothecae given off a tubular, torturously creeping hydrorhiza. Hydrotheca tubular, sessile on the hydrorhiza for about half its length then becoming free and bent outwards, free part up to 1 mm long. Upper surface of the fixed part of the hydrotheca transversely ridged. Hydrothecal margin smooth and slightly evened.
Gonothecae aggregated into a cylindrical structure of tangled appearance (coppinia) adherent to the substrate. Accessory tubes of the coppinia long and twisted, overtopping the gonothecae. Gonothecae closely packed, slipper-shaped, each with a terminal aperture through which larvae are released.
Colour: Usually bright yellow but may be straw-coloured.
Cosmopolitan.
Subtidal, growing on hydroids or algae with a firm cuticle e.g. Caulerpa.