The Nature and Significance of the Pedicleforamen ofLeptaenaDalman

Abstract

In the brachiopod family Strophomenidae, it is recognized that various genera, of whichLeptaenaDalman is a good example, may possess a foramen enclosed within the umbo of the ventral valve, near the apex of the pseudodeltidium (see Text-fig. 2 A). Such a foramen is presumably a pedicle-aperture, and bears a superficial resemblance to that of certain Telotremata in which the young pedicle emerged through the open delthyrium and subsequently resorbed the apex of the ventral valve and became enclosed dorsally by the deltidial plates. In the young stages ofLeptaena, on the other hand, the foramen was entirely supra-apical and enclosed within the ventral protegulum and nepionic shell, though sometimes it later suffered resorption of its dorsal margin so as to become bounded by the pseudodeltidium.