THE STROMATOPOROID ANIMAL REVISITED - BUILDING THE SKELETON

Modern coralline sponges secrete a skeleton by means of a basal pinaco derm, intracellularly, or inside the soft tissue on an organic matrix. The examination of terminal growth surfaces of stromatoporoids indica tes that soft tissue in laminate and amalgamate forMS occupied the upp er galleries and that the skeletal elements were secreted within the s oft tissue on an organic matrix. The stromatoporellids and clathrodict yids secreted the skeleton in modules that are homologous to the chamb ers of a sphinctozoan. In stromatoporellids the module was bounded by a floor that formed the upper layer of the tripartite lamina below and a roof that became the lower layer of the next lamina; it further inc luded the intervening pillars. In clathrodictyids the module had only a roof and pillars, and the laminae are single layers. Other stromatop oroids may have secreted their skeletons at the base of the soft tissu e and had minimal occupation of the skeleton.