TERMS USED IN DESCRIBING MOLLUSKS 
Abductor muscles: Muscles which move parts away from the 
axis. 
Adductor muscles: Muscles which draw parts together; oppo- 
site of abductor. 
Aperture: Opening of the spiral shell. 
Bilateral symmetry: Having two equal sides, divided by a 
central axis. 
Branchie: Gills, or breathing-organs; organs subservient to 
respiration through water. Same as ctenidia. 
Buccal mass: The mouth-parts as a whole; the organ of pre- 
hension and mastication of food; the pharynx: present in all 
mollusks except lamellibranchs. 
Canal: A narrow prolongation of the aperture of a spiral shell. 
Carinated: Ridged as if keeled; having a keel. 
Cinereous: Ash-gray; having the color of wood-ashes. 
Cirri, plural of Cirrus: Filamentous appendages. 
Columella: An upright pillar in the center of most of the uni- 
valve shells, round which the whorls are convoluted. 
Conerescent : Growing together; uniting. 
Cordate : Heart-shaped. 
Coste, plural of Costa: Ridges of a shell. 
Crenulated: Having a series of notches; marked as with 
notches, as the indented margin of a shell. 
Crystalline style: A transparent gelatinous substance of un- 
known function, which fills, at times, the stomach-parts of certain 
mollusks. 
Ctenidia, plural of Ctenidium: Gills, or breathing-organs, 
adapted to water-respiration. 
302 
