Glossary of Morphological and Anatomical Terms
band - A distinguishable increment of growth on a shell.
base of brachial process - Proximal part of pentameroid brachial process attached dorsally to outer plate and ventrally to inner plate homologue of base of brachiophore crus.Fig.365.
beak angle - Angle subtended between commissural plane at the hinge axis and line bisecting beak of astrophic ventral valve as seen in lateral profile; defined as straight (beak angle, 0 to 20°), inclined (20° to 30°), suberect (30° to 70°), erect (70° to 90°), incurved (more than 90°); corresponds to orthocline-anacline condition of strophic shells.Fig.285.
beak ridges - More or less angular linear shell elevations extending from each side of umbo so as to delimit all or most of cardinal area.
bema - Raised area of secondary shell originating near anterior ends of inner socket ridges in some plectambonitoids; may be elevated marginally or divided by radial ridges.Fig.344_2.
bifurcate condition - Vascula lateralia split into anterior and posterior branches immediately beyond point of leaving body cavity.
bilacunar - Long reflected loop typical of adult Kingena and related genera, with a lacuna in the dorsal segment of each ascending lamellae defining a pair of mediovertical connecting bands extending between the median septum and transverse band descending lamellae still united to the median septum.
bilateral - Long reflected loop typical of adult Laqueus and related genera, with two pairs of connecting bands, lateral and laterovertical.
biseptum - Double septum in ventral valve formed by union of dental plates.
bisulcate - Alternate folding resembling parasulcate condition but with median fold of dorsal valve indented by median sulcus.Fig.289.
blister - Space and enclosing curved partition of secondary shell in umbonal and delthyrial chambers of some spiriferides, productides, and pentamerides; formed by sporadically migrating outer epithelium.Fig.372.
body cavity - Principal part of coelomic space, situated posteriorly, bounded by body wall and containing alimentary tract, nephridia, and other organs.Fig.1.
braceplates - Narrowly diverging septa extending anteriorly of dorsal adductor muscle scars in some strophodontids.Fig.369.
brachia - Two armlike projections from either side of mouth segment of lophophore variably disposed but symmetrically placed about mouth.Fig.1.
brachial base - See inner socket ridge.
brachial branches - Narrow elevations of secondary shell within brachial ridges and converging anteromedially.
brachial cavity - See mantle cavity.
brachial lamellae - Calcareous support for lophophore See brachidium and brachial platform.
brachial loop - See loop.
brachial muscles - Muscles in small brachial canal of inarticulate genera, arising from connective tissue at proximal ends of canals extending along their length.
brachial plate - One of pair of subvertical plates constituting pentameroid cardinalia and including inner plate base of brachial process and outer plate.
brachial platform - Raised area of secondary shell originating near alae in dorsal valves of some plectambonitoids that may be elevated marginally.Fig.344.
brachial process - Anteriorly directed blade or rodlike projection from pentameroid cardinalia comparable with crus.
brachial protractor muscles - Pair of muscles in craniids that assists movements of lophophore located anteromedially on dorsal valve.Fig.374.
brachial retractor muscles - Pair of small muscles in dorsal valve of discinids and craniids, located lateral to anterior adductor muscles.
brachial ridges - Paired narrow elevations of secondary shell extending laterally or anteriorly as open loops from dorsal adductor muscle field of some articulated brachiopods.Fig.345.
brachial valve - See dorsal valve.
brachidial net - Calcareous netlike structure uniting the crura and jugum to the floor of the dorsal valve.Fig.341.
brachidium - Calcareous support for lophophore in form of loop or spires.
brachiophore bases - See brachiophore plate.
brachiophore plates - Basal (dorsal) parts of brachiophores that join floor of valve.Fig.329,Fig.365.
brachiophore process - See brachiophore.
brachiophores - Blades of secondary shell projecting from either side of notothyrium and forming or in close association with inner socket ridges.Fig.329.
brachiotest - Thin, granular layer overlain by secondary fibers in calcareous ribbons (lamella) of loops and spiralia secreted by densely filamentar, outer epithelium.Fig.29.
brephic - Juvenile stage in shell development following secretion of protegulum best seen on ribbed valves where it can be distinguished from protegulum by presence of growth lines and from neanic shells by absence of radial ornament.
breviseptum - Dorsal median septum not fused posteriorly with cardinal process.
bridge - Posteromedian part of marginal flange of thecideoid dorsal valve free of valve floor.
brush - Many fine radiating tubular extensions of proteinaceous membrane, which permeate a thin canopy of primary shell separating periostracum from distal head of caecum of terebratulides, thecideidines, and spiriferides.Fig.31.
buccal plate - Small, variously shaped, but bilaterally symmetrical, posteriorly concave plates, normally loose within complete shells of spiriferids, but exceptionally placed posteromedially between spiralia and close to jugal processes possibly discrete supporting piece for the mouth region of the lophophore.Fig.342.
