Dentitheca alata (Bale, 1888)

Hydrorhiza very wide, flat and ribbon-like with very strongly marked, dark coloured flexion joints extending towards middle of the hydrorhiza.

Stems short, perisarc thick, beginning with 1 - 2 ahydrocladiate internodes with deeply incised nodes. Internodes throughout the stem short, with strong opposed V-shaped joints and a secondary constriction in the internode just above the hydrocladial apophysis. Hydrocladial apophysis short, ending in a slightly oblique distal joint.

Hydrocladia alternate, given off near middle of the cauline internode, each bearing 2 - 3 hydrothecae. Hydrocladium beginning with a very short athecate internode, internodes thereafter alternately thecate and athecate but sometimes two short athecate internodes inserted between the thecate internodes. Hydrocladial nodes deeply incised, thecate internode with a transverse to slightly oblique proximal and strongly oblique distal node. Thecate internode completely occupied by hydrotheca. Abcauline hydrothecal wall strongly sinuate, adcauline wall set well down into the internode, base flat. Margin with two broad, backwardly reflexed lobes.

Nematothecae all of same shape and size, bases robust, cups slightly excavated on the adcauline side, one proximal on each stem internode opposite hydrocladium, another on the apophysis of the stem, but not axillar; one median on athecate internode; thecate internode with one median, halfway along abcauline wall of the hydrotheca and set on a broad shelf, and two laterals in the concavity below hydrothecal margin, facing upwards to margin.

Gonotheca replacing a hydrocladium near base of the stem; very large, flattened, elongate oval, narrowing to base, no definite pedicel, maximum width from about the distal third to top, distal end rounded, no definite orifice. Male gonophore oval, surmounted by a cap.