Typically large (> 40 mm diameter) colonies of hemispherical to ovoidal or spheroidal shape which when sectioned exhibit conspicuous concentric layering. Colonies are composed of numerous cup-shaped subcolonies fused at their edges. The surface appearance of colonies varies according to the developmental state of the constituent subcolonies: colonies with fully developed subcolonies are covered by ridges in a polygonal pattern, each ridge marking the junction between two subcolonies; colonies with partly developed subcolonies have a relatively flat surface with indistinct polygons marking subcolony boundaries; colonies budding new subcolonies have polygonal ridges with small, subcircular subcolonies developing on their tops. Lower surfaces of subcolonies are transversely wrinkled, and boundaries between fused subcolonies are strongly corrugated (as seen in thin sections and some fractured specimens). Upper surfaces of subcolonies are covered by the polygonal apertures of autozooids and kenozooids.
Autozooids are tubular with apertures about 0.11 mm in diameter, sometimes slightly salient and arranged in indistinct radial rows. Internally, autozooecia occasionally have transverse partitions (diaphragms).
Kenozooids are also tubular with polygonal apertures but the apertures tend to be slightly smaller and less prominent than those of the autozooids.
Gonozooids are developed at the centres of a minority of the cup-shaped subcolonies. They are distinguished as flat areas formed by smooth calcification (exterior wall) that is pierced by scattered, subcircular autozooidal apertures. Internally, vertical septa-like walls may incompletely subdivide the gonozooid.
Four cyclostome bryozoan species with large, globose colonies occur in the Coralline Crag Formation: Blumenbachium globosum, Meandropora aurantium, M. tubipora and Multifascigera debenensis (see Balson & Taylor 1982). The two species of Meandropora can be readily distinguished from B. globosum by their columnar subcolonies (fascicles), giving vertically sectioned colonies a radial fabric unlike the concentric layering seen in the latter species. Known rarely and only from the Ramsholt Member, Multifascigera debenensis has polygonal subcolonies with fascicles of zooids arranged in a stellate configuration and does not develop the ridged colony surface characteristic of B. globosum.
Pliocene, Late Zanclean–Early Piacenzian, Coralline Crag Formation, Suffolk, UK (Balson & Taylor 1982); ‘Scaldisian’ of the Scheldt Estuary, The Netherlands (Lagaaij 1952); ‘Rédonian’ (Early Pliocene) of Saint-Denis-d’Oleron, Charante-Maritime, France (Buge 1957).
Also found as a derived fossil in the Red Crag of Suffolk and Essex.