Cross Section of Mussel Shell (IMAGE) University of Chicago Medical Center Caption Cross section of a mussel shell showing its thickness. The holes show where samples were drilled to analyze its composition. Credit Cathy Pfister, University of Chicago Usage Restrictions None License Licensed content 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.