Lytocarpia angulosa
Hydrorhiza a bundle of thin, fibrous stolons; colonies of single, straight stems to 500 mm high and 2 mm wide at base, prosegment long, polysiphonic, ahydrocladiate, comprising numerous parallel tubes, some running almost to tips of branches; upper stem region bearing single plumose hydrocladiate branches to 30 mm long in verticels of three; branch internodes short, nodes oblique, faint.
Hydrocladia alternate, long, close-set, inserted in front of frontal tube of branch, internodes short, nodes slightly oblique, distinct to absent; no intranodal septa.
Hydrotheca irregularly hemispherical, anterior adcauline wall strongly convex, lower wall gently rounded, a concavity between two large knots of perisarc separating the two wall sections; a thick intrathecal septum passing from base of mesial nematotheca obliquely forward two thirds distance into hydrotheca, terminating in a knot of perisarc. Margin circular with a single, short mesial abcauline cusp connecting with intrathecal septum followed by three pairs of broad, low lobes, the first pair slightly more acute than others.
Mesial nematothecae of two distinct lengths on different colonies: long nematotheca tubular, arching over hydrothecal margin, terminal orifice small, excavated, base of nematotheca broad at junction with hydrotheca, a secondary orifice, sometimes absent, just above hydrotheca, a small foramen connecting base with hydrotheca; short nematothecae may or may not overtop hydrothecal margin, base same as that of long nematotheca, orifice excavated , often connecting with secondary orifice above hydrotheca. Lateral nematotheca triangular, extending to and sometimes overlapping hydrocladial node; orifice broad, a small posterior foramen connecting with hydrocladium. Polysiphonic tubes of stem and branches with rows of oblong nematothecae, each with a single terminal orifice. Numerous pseudophylactocarps arising at intervals from the outermost polysiphonic tubes of stem and branches to just above first hydrocladium; pseudophylactocarps short, lax, comprising up to 20 short segments separated by deeply constricted nodes, each segment with three long, tubular nematothecae, terminal orifice of nematotheca sinuous, sometimes minutely crenulated; nematotheca containing a battery of large nematocysts.
Colour: Stems light brown, hydrocladia pale yellow-brown.
Indian Ocean, Indonesia and tropical Australia.
Subtidal, on sandy or gravelly substrates.