Of these last, 575 species inhabit tropical seas, 350 the seas of temperate, and 75 the seas of cold climates. XIII. Fossil Elk of Ireland, or _Cervus megaloceros_. (Plate LXXI.)--The shell-marls of Ireland contain in abundance the bones of an animal, which like the Dodo, was once contemporary with the human species, but has long been extinct: the last individuals of the race were, in all probability, exterminated by the early Celtic tribes. The remains of this noble creature generally occur in the deposits of marl that underlie the peat-bogs, which are apparently, like those of Scotland, the sites of ancient lakes or bays. In Curragh immense quantities of these bones lie within a small area; the skeletons appear to be entire, and are found with the skull elevated, and the antlers thrown back on the shoulders, as if a small herd of these Elks had sought refuge in the marshes, and had been engulfed in the morass, in the same manner as the Mastodons of America. (See description of Plate LXXIV., ante, p. 167.) This creature far exceeded in magnitude any living species of elk or deer. The skeleton is upwards often feet in height to the top of the skull, and the antlers are from ten to fourteen feet from one extremity to the other. The fine perfect skeletons in the British Museum, College of Surgeons, and in the Museum at Edinburgh, render a particular description unnecessary. The bones are generally well preserved, of a dark brown colour, with patches of blue phosphate of iron. In some instances they are in so fresh a condition, that the hollows of the long bones contain marrow having the appearance of fresh suet. Remains of this majestic animal have been found collocated with ancient sepulchral urns, stone implements, and rude canoes, in such manner, as to leave no doubt that this now extinct deer was coeval with the early human inhabitants of these Islands. Its bones and antlers have been found at Walton, in Essex, associated with the remains of the Mammoth, or fossil elephant.[122] [Footnote 122: Wonders of Geology, p. 134.] XIV. Fossil Infusoria--_Infusorial Earths_.--In the note on Foraminifera some account is given of various rocks composed of the fossil remains of those minute animals; but the durable relics of the yet more infinitesimal organisms designated by the terms _Infusoria_, or _Infusorial animalcules_, form deposits of equal interest and importance. Strata of great extent and thickness are wholly, or in great part, made up of innumerable layers, consisting of the aggregated siliceous cases or shields of Infusoria: and similar structures are found to be the chief constituents of the white earthy deposits of lakes, rivers, and basins of brackish water, in every part of the world.