It appeared that in chitons the curvature of (1) the leading surface varied from 70° to about 90° and (2) the trailing surface from 40° to about 90°. In the limpet studied both the leading and the trailing surface showed a curvature of more than 100°. In all species strongest curvature was apparent in the lower half of the leading surface. In chitons the leading surface may slightly be recurved close to both the base and the tip of the tooth.