The North Devonian beds, which extend from the coast as far south as the latitude of Barnstaple, consist of slates, grits, and sandstones which, it is believed, judging from the organic remains in them, were formed in shallow water and near shore. Their lower strata, the Foreland grits, Lynton beds, and Hangman grits, contain some fossils and various kinds of coral. But the Middle beds, the Ilfracombe and Morte slates, are much richer in animal remains; of which perhaps the most remarkable are primitive palaeozoic fish, such as the very curious armoured _pteraspis_; while corals and bivalve shells are abundant and characteristic. The Upper Devonian is less fossiliferous, but contains some large trilobites, various marine shells, and some land-plants. The South Devonian, which covers nearly all South Devon and a large part of Cornwall, is somewhat different in character, consisting chiefly of slates, with coralline limestones, varied by volcanic outcrops or elvans--a word said to be of Cornish origin, and meaning "white rock." To judge from its fossils, it was deposited in deeper water than the contemporary beds in the north of the county. The Lower and Middle beds are also far richer in animal remains; and the Middle Devonian of the south, which is the most typical of the series and includes the limestones of Plymouth and Torbay, is crowded with shells, trilobites, and corals. Among the shells, bivalves--such as _Stringocephalus_, which occurs only in the Devonian formations--spiral univalves, and corals are very abundant. There are also many crinoids, distinct from those of the carboniferous limestone, while perhaps the most characteristic form is the rare and curious _Caleola sandalina_, differing from all other corals in having an operculum. There are not many varieties of trilobite, but the large _Brontes flabellifer_ is not uncommon. [Illustration: Logan Stone, Dartmoor] The Lower beds of this series contain fewer organic remains, although a good many fossils are found, including fragmentary remains of various fishes which have not yet been identified. The Upper Devonian is, on the whole, very poor in fossils.