Shell Cross-Section (image) University of Washington Caption This image shows a magnified cross-section of a shell. The lines in the outer layer come from growth during low tides, and help to put a time on the temperature measurements. Credit M. Carré / Univ. of Montpellier Usage Restrictions With credit Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.