LOWER SILURIAN. UPPER SILURIAN. 140 MANUAL OF GEOLOGY. Wenlock Shale. Hard flaggy beds and thin shales, in places slaty, with occasional beds of sandstone ; fossils resembling those above. Loc. Wenlock, Dudley, Walsall, Malvern, Usk, &c. Wenlock Group. Woolhope Beds. Denbighshire Grits and Tarannon Slates. ( Dark-grey, semi-indurated limestone, with much carbonate of lime in veins, and oc- ! casional bands of argillaceous nodules, / &c., also sandy beds in places ; lUcenus \ (Bamastus) Barriensis, Orthis Davidsoni, I 0. degantula, var. Loc. Woolhope, I Walsall, &c. 'Thin-bedded flaggy sandstones and slaty beds ; fossils comparatively rare in - places, especially in the gritty beds. Loc. Flintshire, Denbighshire. Tarannon . river-banks, &c. Upper Llando very. Lower Llando very. Caradoc or Bala Kocks. Grey and yellowish sandstones (occasion ally conglomerates), with bands of lime stone ; rich in organic remains, especi ally Brachiopoda ; Pentamerus oblonxjus, Rhynchonellce^ Orthides, &c. Loc. May Hill, Shelve, Tortworth, &c. Hard sandstones, conglomerates, and flaggy shaly beds ; the fossils closely allied to those of the Upper Llandovery series ; but distinguished by Pentamei'us (Strick- landima) lens, and by unconformity. 'Shelly sandstones, shales, and slaty beds, with quartzose grits, conglomerates, and occasional limestone or calcareous bands; fossils numerous, especially Echinoder- mata, Crustacea (Trilobites), Polyzoa, and Brachiopoda; of the last nearly fifty species, including Orthis Actonice and 0. flabellulum. Loc. Caradoc, Hor- derley, Norbury, Bala, Snowdon, Wex ford, Kildare. Llandeilo Flags. 'Dark-grey flagstones, occasionally calcare ous, with black slates containing Grap- tolites, &c. The Llandeilo flags contain Lingvlce, OboleUce, Discince, and Orthidcc, with the well-known Trilobites Ogygia Buchii, Asaphustyrannus, and Trinucleus concentricus. Loc. Llandeilo, Builth, &c. Arenig or Stiper- stone Group. Dark slates, shales, and flags, and thin sandstones (developed in the Arenig mountains), associated with porphyry. / yEylina, Illcenopsis, Barrandia, lUcenus, N CaLymene, Conularia, Theca, and many I genera of Rhabdophora. Loc. St. I David’s, Tremadoc area, Stiperstones, \ Skiddaw, &c.