Differential interference contrast (DIC) light micrograph of the radula of a common periwinkle (Littorina littorea). These marine snails are found in rock pools and on rocky, sandy and muddy coasts. The marine snail radula surface is a tongue-like organ found in molluscs. Gastropods have elaborate radulas used primarily for gathering food. A gastropod radula is a toothed chitinous ribbon studded with longitudinal rows of chitinous and recurved teeth, the cuticula. It is used to rasp and scrape diatoms and other microscopic algae off rock surfaces and other substrata. Magnification: x200 at a print width of 10 centimetres.