Spirula is the only genus of squid with an internal shell, a relic of their ammonoid ancestors. When Spirula die their fragile shells float to the surface and are collected on the beaches as "rams horn shells" - this one is encrusted with barnacles.
Traditional Norwegian knitting patterns, Selbu mittens. 1. Værhorns-rosa (Rams Horn rose), 2. Endløs-rosa (Endless rose), also called Grankvist (spruce branch), 3. Kinn'tyrill-rosa (though I have also seen this named Rams Horn rose)