Carboniferous Period, 359-259 million years B.P. A group of two bifacial white Pecopteris sp. fern specimens. 789 grams total, 18.5 cm (7 1/3 in.). St. Clair, Pennsylvania, USA. Acquired 1980s. Pradi collection, Boston, USA. These fern fossils are verymon from coal mining areas around the world. However, it is the unique state of preservation of the white on the black shale that gives the St. Clair ferns their beauty and rarity. [No Reserve]