The fauna boring into Montastrea annularis includes sponges" bivalves, sipunculid and polychaete worms and barnacles. Sponges.and spionid polychaetes are most important in hard tissue destruction and

Stromatoporoids were a subphylum of the Porifera whose soft parts can be reconstructed by comparisons with the living sclerosponges Merlia and Astrosclera. The living tissue was confined to the upper surface and penetrated only short distances into the coenosteum. Astrorhizae are traces of an excurrent water canal system that interfered with the secretion of the skeleton in some stromatoporoids but was entirely above the hard tissue in others. The stromatoporoid skeleton was composed of trabecular or spherulitic aragonite. Calcitization and dissolution of the aragonite proceeding from the centers of calcification outward account for the microstructures (fibrous, compact, tripartite, ordinicellular, cellular, melanospheric) commonly observed in the calcite skeletons of fossil stromatoporoids. Reconstructions showing the proposed relationship of the soft tissue to the hard tissue of Labechia, Stictostroma, Actinostroma and Stromatopora are presented.

Paleoecologists studying Paleozoic reef-builders have interpreted their growth forms as responses to conditions of depth and turbulence in reef complexes. Comparison of the shapes of Paleozoic stromatoporoids and corals with the growth forms of modern scleractinians has been used to reconstruct Paleozoic conditions. A review of shape zonation on modern reefs indicates that no general pattern is applicable to all reefs and variations in shape are the result of the interaction of many environmental factors with the genetically dictated growth pattern of the coral. In most zones of a reef a wide range of shapes co-exist. The growth forms of corals on modern reefs are not a simple vegetative response to the many environmental parameters that have been shown to influence form, but are constrained by phylogenetic and developmental influences as well as functional ones.Interpretations of the environments of western Canadian and other mid-Paleozoic reefs have been based on the growth forms of stromatoporoids. The environmental significance of the shapes has been deduced from comparison with the shapes of modern scleractinians, functional morphology, nature of the enclosing sediment, position of growth, position within the reef, and diversity gradients. The validity of these criteria is open to question and considerable doubt remains concerning the significance of the growth forms. The shapes of reef animals are not specific guides to environments of modern reefs and should not be expected to be guides for ancient ones.

On the south margin of the reef complex, five assemblages of stromatoporoids are defined in the 500 m thick Frasnian succession. The first, in the lower part of the Flume unit, consists of five species that occupied a platform environment in the initial Devonian sea. The second assemblage, of the upper Flume and upper Cairn interval, contains the greatest number of species and represents a patch reef environment formed as relief between the reef complex and basin developed. The third assemblage, of the lower Pecchee Member, contains few species of dominamly tabular-encrusting stromatoporoids that occupied the complex margin at the time of maximum relief and is contained in a megabreccia bed derived from the edge of the complex. The fourth, in the upper part of the Peechee Member, is associated with the close of reef growth at the complex margin and is found in an upper megabreccia bed and bioherms that grew on its surface. The fifth assemblage, of the Arcs Member, represents the return to a patch reef environment that supplied carbonate sand to form this member. Stromatoporoid diversity is low in assemblage I, increases to a maximum at the bottom of assemblage II, and decreases through the upper parts of assemblages II, III, and IV. It is again high in assemblage V. Low values of diversity are interpreted as reflecting shallow water environments of high unpredictability.Twenty-two species of the stromatoporoid fauna are described or re viewed. The following new taxa are established: Sticlostroma jasperense, Taleastroma steleforme, Hermatostroma haultainense, Stachyodes jonelrayi.

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