Ammonite Fossil Bead measures approximately 2.5 inches by 1.75 inches by 11mm in size, the Ammonite Fossil is a half specimen showing the shell containing a spiraling progression of ever larger chambers divided by thin walls called septa, the pattern of the septa is reflected on the outside of the shell called sutures and this fossil`s sutures are fern-like which classify the septa as Ammonite. The name `ammonite` originates from the Greek Ram-horned god called Ammon. This Ammonite fossil shell is a particularly beautiful spiral form which has been drilled from side to side as shown in the photograph. Ammonite first appeared in the late Silurian to early Devonian Periods (~400 million years ago). Only some 10% of species survived the Permian Extinction, and their ultimate demise coincided with that of the dinosaurs in the K-T extinction event that closed the Cretaceous Period. Imagine owning a natural Ammonite Fossil which has been in the earth for 400 million years.