Cystodictya

Diagnosis. Bifoliate colonies, strap-like, branching in plane of mesotheca. Autozooecia with peristomes and lunaria. Ridges between autozooecial rows lacking. Mesotheca thin to moderately thick, indistinctly laminated to granular-prismatic, with low ridges, running parallel to ranges of autozooecia. Autozooecia teardrop-shaped at their bases, quadrate in transverse section; partly isolated by boxlike vesicles; recumbent portion short; blunt proximolateral hemisepta at zooecial bend, indenting zooecial cavity and producing slight hookshaped appearance of autozooecia in deep tangential section. Diaphragms lacking. Walls laminated; boundary serrated, tubules in cortex. Lunarium in exozone, light coloured, laminated, some with core and proximal rib. Compound range walls thin in endozone with dark boundary continuous into dark central layer of mesotheca; thick in exozone with many flexures and irregular tubuli. Vesicles small, boxlike, in endozone; low blisters in inner exozone; stereom in exozone; laminated with tubuli and flexures.

Remarks. Cystodictya Ulrich, 1882, differs from Sulcoretepora d’Orbigny, 1849, in possessing teardrop-shaped apertures, straight mesotheca and autozooecial walls, which are distinctly tripartite in Sulcoretepora and more homogenous in Cystodictya. Furthermore, Cystodictya possesses hemisepta, which are absent in Sulcoretepora. Cystodictya differs from Dichotrypa Ulrich in Miller, 1889, in lacking acanthostyles in its exterior stereom. Occurrence. Middle Devonian – Pennsylvanian; worldwide.

Type species. C. ocellata Ulrich, 1882, by original designation. Lower Mississippian; Kentucky, USA.