Anterior end - the shorter end of the shell as measured from the umbo; also considered the front end
Beak - the raised art of the dorsal margin of the shell; also called the umbo
Beak cavity - the depression or pocket on the inside of each valve leading into the beak
Beak sculpture - the raised loops, ridges, or bumps on the umbo
Chevron - a V shaped marking
Compressed - flattened or pressed together laterally
Concentric - having a common center
Distal - away from the center or origin
Dorsal - referring to the top part of the shell where the hinge is located
Elliptical - having the form of an ellipse, or oval
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Extirpiated - locally extinct
Growth lines - darkened lines on the surface of the shell indicating periods of rest during growth
Hinge - the elastic part of the shell that unites the valves along the top of the shell
Inflated - swollen or expanded
Inderdentum - a flattened area between the pseudocardinal and lateral teeth
Iridescent - exhibiting rainbow colors
Lateral teeth - the elongated teeth along the hinge line off the shell
Left Valve - the left half of the shell when the dorsal hinge is facing up and th anterior end is directed forward (away from the collector)
Nacre - the interior layer of the shell, usually white, pink, salmon, or purple and iridescent
Oblong - having the shape of or resembling a rectangle or ellipse
Ovate - egg-shaped
Pallial line - a liniar depression on the inside of the shell
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Periostracum - the outside layer or covering of the shell
Plications - folds
Posterior end - the longer end of the shell as measured from the umbo; also considered the back end;also the end with the siphons, usually sticking above the stream bottom
Posterior ridge - the ridge on the back half of the valve running from the umbo to the posterior ventral edge
Posterior slope - the area along the dorsal part of the shell between the posterior ridges of the valves
Pseudocardinal teeth - the triangular, often serrated, teeth located on the anterior-dorsal part of the shell
Pustule - a bump or raised knob on the outside surface of the shell
Quadrate - square
Right valve - the right half of the shell when the dorsal hinge is facing up and th anterior end is directed forward (away from the collector)
Serrated - notched or grooved
Shell margin - the circumference of a valve outline when laid flat; also known as the edge
Solid - thick or heavy
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Striated - marked with lines or grooves
Sulcus - the shallow depression or furrow on the outside surface of the shell
Truncate - having the end shortened or squared off
Tubercle - a pointed, rounded, or knoblike projection on the shell
Umbo - the inflated dorsal part of the shell
Valve - one of the two halves of the shell
Ventral - referring to the bottom edge of the shell
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