Glossary of Morphological and Anatomical Terms

falciform - Crura arising on dorsal side of hingeplates and projecting into dorsal valve as broad,bladelike processes.
false cardinal area - Previously used for any poorly defined cardinal area or pseudointerarea.
false pedicle groove - See intertrough.
fascicostellate - Ornament of costae and costellae arranged into bundles.Fig.297.
fastigium - Dorsal radial fold resulting from commissural flexure in many spiriferides.
fenestrae - Concentrically aligned, orthogonal openings in anterior part of punctatrypidshells, extending from interior through primarylayer to exterior; closed posteriorly by shell secretion.Fig.259,Fig.260.
fibrous layer - See secondary layer term commonlyused as alternative for secondary layer of articulatedbrachiopods when exclusively composed of calciticrods (fibers) with lenticular or anvil-like cross sections.Fig.242.
filum - Fine concentric ridge of variable persistence ornamenting external surface of shell.Fig.292.
fimbria - Spinelike projection from spiralia or jugum also used for spinose projection onmargin of growth lamella as in Spinilingula.Fig.336.
flange - Incurved lateral and anterior margins of both valves.
flanges - Pair of small, laterally projecting flanges that appears very early in loop ontogenyon the posteroventral edge of the septal pillar oflaqueoids and some platidioids.
flanks - See lateral slopes.
flap - See posterior flap.
flexure line - Line extending from beak to anterior border of both ventral propareas in some linguloids,marked by deflection of growth lines.Fig.286.
fold - Major elevation of valve surface, externallyconvex in transverse profile and radial from umbo.Fig.288,Fig.289.
foramen - See pedicle foramen term commonly usedwith this meaning.Fig.285.
foraminal sheath - See pedicle sheath.
foraminal tube - See pedicle tube.
free - Animal not attached to substrate.
free spondylium - Spondylium unsupported by septum.
frenuliniform - Growth stage of loop characterized by a lacuna in each ascending lamella.
frill - Relatively large growth lamella projecting well beyond general contour of valve, deposited by margin of highly retractile mantle.
fulcral plate - Small plate raised above floor of dorsal valve extending between posterior margin and brachiophore plate or inner socket ridge and socket plate and forming floor of socket.Fig.332.
furrow - See interspace.
fused hinge plates - Hinge plates joined together along midline with no development of septalium.Fig.330_3.