Brachial Valve: The valve to which the lophophore is attached, as well as the lophophore support (brachidium), if any; also the valve bearing the sockets.  The brachial valve commonly is smaller than pedicle valve.  Also called the dorsal valve.

Brachidium: A hard or calcareous internal lophophore support, commonly resembling a loop or spires, which attaches to the posterior part of the brachial-valve interior.

Cardinal Process:  A blade or knobs of shell material located in the middle of the posterior end of the brachial-valve interior; used for diductor-muscle attachment;  see Hinge line

Costae:  Ridges of exoskeleton material forming ornamentation on the exterior surface.  May be co marginal or at some angle to the growth margin (radial, spiral, etc.).  Also called a rib, especially in a brachiopod.  In an ostracode, a costa is not as prominent as a carina.

Fold: A major rounded elevation of exterior and interior shell surfaces along the midline that radiates from the umbo; generally a feature of the brachial valve.

Hinge line:  The posterior margin where the two valves of a shell articulate.

Lophophore:  A coiled fleshy organ in the mantle cavity that is rarely, if ever preserved in fossil specimens.  It is typically attached to the interior of the brachial valve.  Two arms, or brachia, are edged with fringelike filaments that create currents to bring food and oxygen to the mouth of the animal.  The two lophophore arms, in some cases, were supported internally by calcareous brachidia.

Pedicle: A fleshy stalk attached internally to the pedicle valve and protruding from the posterior end of many brachiopods through the pedicle opening; typically used to permanently attach the shell to a hard surface.

Pedicle valve:  The valve to which the pedicle is attached and which bears the teeth; it is the ventral valve and generally is larger than the brachial (dorsal) valve.

Sulcus:  In an ostracode, an elongate valley or depression in the valve
surface.  In a pelecypod, a major, radial infolding of the shell.  In a
brachiopod, a major depression of the inner     and outer valve surfaces along the midline, externally concave in profile, radiating from the umbo, and generally associated with the pedicle valve called the sinus in older literature.

Valve:  One of the two shells that form the carapace or exoskeleton of an ostracode or a phyllocarid or the shell of a pelecypod or brachiopod.