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GLOSSARY. 
Appuctor Muscies. The muscles which connect the valves 
and pull them together. 
APERTURE. The opening in a spiral shell. 
Apex. The tip of the spire. 
Beaks. The first formed part of a bivalve shell. See figure 
2. Also called the Umbo. 
Brvatve. A shell composed. of two parts or valves, such as 
the Oyster and Clam. 
Canau. A narrow prolongation of the aperture of a spiral 
shell, for the protection of the siphon conducting water to 
its gills. 
CotuMELLa. The pillar around which the whorls or turns 
of a spiral shell revolve. 
Eprpermis. The horny coating which covers the outside of 
some shells. 
Lunute. A heart-shaped impressed area just below the 
beaks. It is prominent in the round clam, or Venus. 
MANTLE. The fleshy or membranous lining of the shell. 
OpercuLuM. A horny or shelly plate closing the aperture of 
a spiral shell. | 
PALLIAL LINE. . The impressed line in the interior of a bi- 
valve shell, where the mantle is attached. See figure 1. 
Pp - 
