40 
PaLuIAL sinus. The bay or indentation in the pallial line, 
where the muscles which retract the siphons are attached. 
See figure 1. Clams with short siphons have no pallial 
sinus. 
SrpHons. The tubes through which water is drawn to the 
gills and mouth of a bivalve, and expelled from them when 
used. 
Spree. All of the whorls of a spiral shell except the last one, 
together form the spire. 
Suture. The line where the turns of a spiral shell unite. 
TreetH. The tooth-like projections upon the hinge of a 
bivalve shell. 
Umepriicus. The cavity in the base of a shell in which the 
columella or axis is hollow; such as Natica heros. 
Umpo. See figure 2. Also called beaks. 
Unrvyatve. A shell composed of one part only, such as the 
Conch. 
VALVE. One of the two parts of a bivalve shell, such as a 
clam. 
Wuorts. The spiral turns of a shell. 
Sd 
