Page:The Zoologist, 3rd series, vol 1 (1877).djvu/149

Rh the thickness of a shilling, will often suffice to preserve the thighbone of an Elephant. It is now generally supposed that many of the rivers of our southern and eastern coasts are but the head-waters of what were once much larger rivers before the severance of the islands from the mainland of Europe. The Thames is thought to have been one of the tributaries of the Rhine; and, as will be noticed in the sequel, it is seldom that oyster-dredging is prosecuted with vigour on the coasts of Norfolk and Suffolk without quantities of bones of extinct quadrupeds being brought to the surface. When the separation in question took place is not altogether clear; that England and Europe were united, however, at the close of the glacial epoch seems pretty certain, else how could such animals as the Elephant and the Lion have reached the British Islands? The probability is that there was a highway at the Straits of Dover, which may have disappeared before the Lions and Elephants died out on British soil.

With the thaw of the glacial period the rivers doubtless became, then and long afterwards, subject to constant inundations, which covered large tracts of country, and formed deposits of sand, loam and clay, in which the animal remains are now found. London, for example, is built on deposits of the ancient Thames; and in many other situations where insignificant streams now exist, the banks are made up of vast beds of débris stretching inland, and containing the bones of both extinct and living animals. Again, deep in the brick-earths of the Thames Valley, at Clacton, Ilford, Grays (Essex), and Crayford, remains representing herds of giant Oxen, Deer, Elephants, Rhinoceroses, &c., have been discovered from time to time, indicating that they had probably been drowned and carried down by inundations of the Thames. In the nature of the animal remains there is a general accord with those of river-bottoms and of the caves, thus showing that they were of the same geological period. But in the brick-earths, or lowermost strata of rivers, it sometimes happens that remains of animals are found distinct from any other species found in the upper beds and in the caves; in consequence, it has been surmised that the brick-earths may have been deposited during pre-glacial times, and therefore contain the animals of that epoch. Some idea of the animals which frequented Wales, South and South-Western England, the Thames Valley, Yorkshire, and the South of Ireland may be gathered from the following:—

In several caverns in Glamorganshire remains of man have been