Ammonite Small 258×320 Medium 517×640 Large 827×1024 Download Tiff Original 1938×2400 | (1.6 MB) Description Ammonite, side view. Where the shell has been partly worn away near the aperture, the complex "suture line" is shown. Keywords ammonite, mollusk, shell Galleries Squid, Octopus, and Nautilus Source: Amadeus W. Grabau A Textbook of Geology (Boston: D.C. Heath & Co., 1920) 314