Top to bottom: Three examples of an extinct species of dasycladacean algae (green algae) from the Middle Silurian section of the Lower Silurian to Lower Devonian Vaughn Gulch Limestone, Inyo County, California.

Top and middle photographs are views of the fossil algal exteriors. Image at bottom is a natural cross-section showing the system of radial canals present within the ancient species of green algae (family Dasycladaceae). Called scientifically Verticillopora annulata. All three images come from a specific scientific publication.