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Taxon
Zygophylax sibogae Billard, 1918
Nomenclature
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Family: LafoeidaeGenus: Zygophylax
SUMMARY
Hydrocaulus flaccid, hyaline, lightly fascicled, polysiphonic tubes almost parallel, running up stem and major branches to just below the distalmost branches.
Branching irregular, more or less in one plane, bifurcations common, a hydrotheca in each fork; perisarc of stem and branches smooth, internodes long, nodes (if present) just above apophysis of branch.
Hydrothecae alternate, facing forward, widely separated along branch, pedicels long and narrow, pointing obliquely upward from a strong, bulbous apophysis, a constriction at junction with apophysis, diameter of pedicel increasing distally to hydrotheca. Hydrothecae long, trumpet-shaped, distally bent perpendicular to proximal axis at two thirds distance from floor; hydrothecal floor clearly demarcated from pedicel by a slightly concave diaphragm pierced by a small central foramen; adcauline wall almost straight to bend then becoming concave to margin; abcauline wall swollen below bend, narrowing into a deep flexure at bend then becoming convex to margin. Margin circular, rim strongly everted, most hydrothecae with up to four slightly everted replications. Perisarc moderately thick.
Nematothecae on adcauline side of apophysis at base of hydrothecal pedicel, variable in length but mostly small, cigar-shaped, diameter of orifice a little less than that of body, some with a long tubular extension with replicated margin, perisarc thin.
Colour: Transparent and colourless (preserved material).