Entobia geometrica Bromley et D'Alessandro, 1984

Type macroboring, substrate calcareous, tracemaker invertebrate.

Diagnosis: Camerate entobian. Apertures of two markedly different sizes; the larger generally unfused, variable in diameter; the smaller spread among the larger ones. Apertural canals very short. Chambers wide, generally polygonal in section in mature growth-phases, separated by thin walls perforated by numerous short intercameral canals that may be fused together. In more juvenile phases the chambers are oval or subspherical, always joined by a distinct intercameral canal. Chambers disposed in weakly developed rows, tending to form a subrectangular network. The dominant growth phase is D; B and C are usually much reduced. The system is developed parallel to the external substrate surface, in usually only one or two tiers.