Based on the pattern from OddKnits (www.oddknit.com/patterns/beach/cockleshell.html). Real cockle shells, like all bivalves, are asymmetric so I'm trying to alter the pattern to make it asymmetric, too. Entered the pattern to check stitch counts and that ridge alignment, but haven't tried knitting it yet.
Shown with a cast-on count of 0 stitches.