| Scientific cross-sections of stromatoporoids--an extinct variety of calcareous sponge--from the middle to upper Devonian Guilmette Formation, Lincoln County, Nevada, a number of miles south of White Pine County, Nevada. Stromatoporoid sponges are among the more common fossil types found in the Guilmette Formation. Scale bars at left of images are one millimeter long (3/64 of an inch). Photograph courtesy Jeffrey Lee Aul; I edited and processed the image through photoshop. |