Structure of Pseudohornera bifida (Eichwald)

The structure of the skeleton of the bryozoan Pseudohornera bifida (Eichwald) is described in detail. The wall structure is composed of a central granular layer flanked by laminated tissue. The granular layer predates the laminated layer. The skeleton is provided with numerous calcareous rods originating from the granular layer. The soft tissues have been reconstructed. The inner epithelium, secreting the skeleton, and the outer, secreting the cuticle, were probably separated by a hypostegal coelomic cavity. The structure of the skeleton in Pseudohornera bifida confirms the position of the Phylloporinidae near the fenestrate cryptostomes, as suggested by recent workers. The relations of the stenolaematous groups provided with granular walls are briefly discussed.