| Top and bottom--Two views of the same chunk of limestone bearing extinct colonial corals from the middle to upper Devonian Guilmette Formation, White Pine County, Nevada. Image at top reveals the coral heads, from which the actual coral animal protruded while feeding; photograph at bottom is a natural longitudinal section, showing extent of the coral colony in vertical orientation through the limestone. The specimens are silicified, by the way, replaced by the mineral silicon dioxide. |