Arborescent - having the size, form, or characteristics of a tree.

Angular - having a bony structure.

Anterior - located near the head in lower animals.

Aperture - an opening, as a hole, gap, or slit.

Benthos - bottom of sea or lake.

Branchial - a breathing organ, as a gill.

Concentric - having a common center.

Cyst - a capsulelike membrane or certain organisms in a resting stage.

Dorsal margin - referring to the top part of the shell where the hinge is located.

Elongate - long or extended.

Extirpated - locally extinct.

Glochidia - a parasitic larva of certain freshwater mussels with hooks for attaching to a host fish.

Gravid - pregnant.

Homogeneous - of the same or similar nature or kind.

Impoundment - to accumulate (water) in a reservoir.

Incurrent - permitting passage to an inflowing current.

Malacology - scientific study of molluscs.

Mantle - a membrane between the body and shell of a mollusk or brachiopod.

Marsupium - a temporary egg pouch.

Midden - piles of freshly cleaned mussels.

Papillae - a small nipplelike projection.

Postbasal - bottom left of a mussel.

Posterior - situated behind a part or toward the rear of a structure.

Siphon - a tubular organ of aquatic invertebrates, by which water is taken in or expelled.

Sporadic - occuring at irregular intervals, having no pattern or order.

Substrates - a surface on which a plant or animal grows or is attached.

Sulcate - having narrow logitudinal indentations.

Sulcus - a deep narrow furrow or groove.

Tubercles - a nodule or swelling.

Ventral margin - the edge near the belly of a mussel.