Fossil Texture of a Strophostylus cyclostomus Snail

While looking at a chunk of Waldron Shale that had a crinoid calyx, the shale split revealing a small fossil fragment. This image was taken while it was under a microscope with a field of view of about 4 mm.

The Strophostylus cyclostomus was described by James Hall in the 1881 Indiana Geological Survey (pages 316-317; Plate 31 Figure 13). "An enlargement of the surface-striae of a full-grown specimen, showing the transverse striae of growth, and the finer revolving lines."

The image was taken with Moto G 2nd generation phone.