Helicoprion is a long-lived genus of extinct, eugeneodontid holocephalid fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls." This fossilized jaw shows the spiral dentures.
Indian Woman with Owl . Blind River, Ontario, Canada -- I've always wondered what she was thinking, considering that the owl is not alive, or could have been sick. For some tribes the owl is a symbol of death -- a taboo to behold.
A cross section of a bundle of nerve fibers. Axons (orange) are wrapped in myelin (purple); an extension of the membrane of glial cells. Myelin has high lipid content, and acts to insulate the axons, causing them to transmit nerve impulses much faster.
Ammonite pavement in Lyme Regis, Dorset, Great Britain - a World Heritage Site. We went fossil hunting at Lyme Regis as kids! I took my husband a few years ago and we only found one fossil! I don't think he believed we used to find loads.