Stromatoporoid cross-sectional shape can be considered as a product of the interaction of three morphological variables: the relative proportions of basal, vertical and diagonal dimensions. The gross arrangement of internal lamination can be superimposed upon the resulting outlines. These shapes are taken to represent cross sections in any vertical plane through the centre of the coenosteum. This simple parameterization scheme is presented in triangular arrays which include the stromatoporoid morphotypes laminar, domical and bulbous, and varieties of them together with forms not utilized by stromatoporoids. Dendroid and irregular forms are too complex to be readily included in the scheme.Smooth and ragged varieties of laminar and domical forms are distinguished and related to sedimentation on the flanks of the coenosteum. Two types of mutual arrangement of latilaminae within the coenosteum are recognized: enveloping, where they completely overlap previous latilaminae, and non-enveloping, where they do not. Laminar4omical-bulbous forms represent a series generated mainly by reduction of the basal dimension. They commonly exhibit enveloping latilaminae except in ragged varieties and some extended domes. Measurement of defined dimensions in the field allows stromatoporoid morphotypes to be plotted onto the triangular arrays and provides a rapid method of displaying the range of forms present.The stromatoporoid skeleton commonly has a concavoxonvex appearance with a flattened concave base and a convex upward upper surface 16-Lethaia 3/78