Monograptus leintwardinensis beds; and the Dinas Bran beds. Lower Ludlow fossils Cyathaspis ludensis, the earliest British vertebrate fossil, was found in these rocks at Leintwardine in Herefordshire, a noted fossil locality. Trilobites are numerous (Phacops caudatus, Lichas anglicus, Homolonotus delphinocephalus, Calymene Blumenbachii); brachiopods (Leptaena rhomboidalis, Rhynchonella Wilsoni, Atrypa reticularis), pelecypods (Cardiola interrupts, Ctenodonta sulcata) and gastropods and cephalopods (many species of Orthoceras and also Gomphoceras, Trochoceras) are well represented. Other fossils are Ceratiocaris, Pterygotus, Protaster, Palaeocoma and Palaeodiscus. Upper Ludlow sub-group The Upper Ludlow sub-group rocks are mainly soft mudstones and shales with some harder sandy beds capable of being worked as building-stones. These sandy beds are often found covered with ripple-marks and annelid tracks. One of the uppermost sandy layers is known as the " Fucoid bed " from the abundance of the seaweed-like impressions it bears. At the top of this sub-group a brown layer occurs, from a quarter of an inch to 4 in. (63 mm to 100 mm) in thickness, full of the fragmentary remains of fish associated with those of Pterygotus and mollusca. This layer, known as the "Ludlow Bone bed," has been traced over a very large area. The Tilestones, Downton Castle Sandstone, and Ledbury Formation shales are occasionally grouped together under the term Downtonian. They are in reality passage beds between the Silurian and Old Red Sandstone, and were originally placed in the latter system by Sir Roderick Murchison. They are mostly grey, yellow or red micaceous, shaly sandstones. Upper Ludlow fossils The common Upper Ludlow fossils include: plants (Actinophyllum, Chondrites), ostracods, phyllocarids, eurypterids; trilobites (less common than in the older Ludlow sub-groups); numerous brachiopods (Lingula cornea, Lingula minima, Chonetes striatella); crustaceans (ostracods); gastropods (Phyllocarida, Platyschisma helicites); bivalvia; and cephalopods (Orthoceras bullatum); and fish (Cephalaspis, Cyathaspis, Auchenaspis). See also References Geologic formations of the United Kingdom Geological groups of the United Kingdom Geologic groups of Europe Ludlow epoch Geologic formations of England Geologic formations of Ireland Geology of Scotland Geology of Wales Silurian United Kingdom Silurian England Silurian Ireland Silurian Scotland Silurian Wales Silurian System of Europe