. Bulletin of the Natural Histort Museum. Geology series. LOWER CARBONIFEROUS BRYOZOA 145. Fig. 58 Rhombocladia dichotoma (M'Coy. 1844) comb, nov. Line drawing of external features: a, obverse surface (BMNH PD9591): b, reverse surface (BMNH PD9593); scale bar = 1 mm. (Visean, Asbian), Carrick Lough, County Fermanagh. 42549, Upper part of the Glencar Limestone (Visean, Asbian), Siilees River, County Fermanagh. M-Coy's original diagnosis. 'Dichotomous; obverse rounded, with about six equal, parallel, slender, longitudinal ridges, in the concave furrows, between which are five rows of
. Bulletin of the Natural Histort Museum. Geology series. LOWER CARBONIFEROUS BRYOZOA 145. Fig. 58 Rhombocladia dichotoma (M'Coy. 1844) comb, nov. Line drawing of external features: a, obverse surface (BMNH PD9591): b, reverse surface (BMNH PD9593); scale bar = 1 mm. (Visean, Asbian), Carrick Lough, County Fermanagh. 42549, Upper part of the Glencar Limestone (Visean, Asbian), Siilees River, County Fermanagh. M-Coy's original diagnosis. 'Dichotomous; obverse rounded, with about six equal, parallel, slender, longitudinal ridges, in the concave furrows, between which are five rows of oval, prominent cells, the marginal furrow on each side free of cells; reverse flat, with numerous, semicircular, scale-like wrinkles, and about six longitu- dinal striae.' Emended diagnosis. Rhombocladia with a ramose zoarium of dichotomising branches oval to elliptical in cross-section. Seven to twelve longitudinal rows of autozooecial apertures open onto the obverse surface. A single superior hemiseptum is developed on the proximal side of apertures and basal diaphragms are rare. Inter- ipertural areas smooth, or with small apertures oval to rhombic in shape; a single large acanthostyle occurs proxi- nally at each autozooecial aperture. Reverse surface barren, with jarallel semi-circular ridges along the length of branches. Description. Zoaria are ramose with dichotomously dividing lattened branches. In cross-section branches are oval to elliptical in .hape, and convex frontally. The largest fragment examined meas- ires in length. Autozooecial apertures open on the obverse surface only, and are irranged into 7 to 12 longitudinal rows. The number of rows along II branch is usually stable until a bifurcation point is reached, where he shape and size of apertures becomes variable and the regularity )f their organization is lost. Uniformity returns distally beyond )ifurcations. Narrow, barren marginal zones on the obverse surface ire common in most z
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