Archerd Shell Collection > Shell Classes > Bivalvia Family Index, page 1
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Overview
The hinge may have a variable number of interlocking "teeth," like notches on a door hinge. Their shape and number serve, in part, to characterize individual species. Because of their utility in fossil identification and dating, such details of shell structure probably have received much more attention than would be warranted by consideration of body plan, alone. The bivalve body plan is quite simple. It has lost a defined head end with pharyngeal glands and radula. Tactile, chemosensory, and visual receptors where present, have migrated to the mantle at the open edges of the shell. With the exception of the Poromyoidea and several other superfamilies in the Order, Anomalodesmata, almost all other bivalves are sedentary filter feeders, that live on minute particles of algae and detritus. The partcles are swept by a powerful ciliary current, aided by muscle contractions, then filtered out on pairs of highly enlarged, plate-like gills ("lamellibranch"). Morton, 1960, states that a typical bivalve can move from 30 to 60 times as much water per hour as its body volume. Cilia further assist the transfer of food particles from the gills to the lip-like "palps," which funnel food particles to the mouth. |
Archerd Shell Collection > Shell Classes > Bivalve Family Index, page 1