Forms in Nature.

AMMONITIDA: Ammonshorne

These spiral-shaped mollusks are an extinct species of cephalopod that thrived in the Paleozoic Age. Their petrified shells were found in great quantity, aggregated into large, rocky formations. Their nautilus-chambered interior compartments are filled with air, diminishing body weight and increasing buoyancy. The range of surface patterns is unusually varied, ranging from mechanistic, chiseled forms to the diaphanous lacy veil of the Ammonite Opulentus (center left). Repetition and regularity make the designs look even more machine-made. The bodies of this species exist as demi-shells: essentially we are looking at mollusks-on-the-half-shell.