There is plenty of evidence about Cambridge of the gradual extermination of species still going on. Indeed, I feel inclined to say that there is no such thing as a Holocene age. I remember land shells being common of which it is difficult now to find live specimens, and my wife[6] has shown how the mollusca are being differentiated in isolated ponds left here and there along the ancient river courses above the town. [6] "On the Mollusca of the Pleistocene Gravels in the neighbourhood of Cambridge," by Mrs McKenny Hughes. _Geol. Mag._ Decade 3, Vol. V, No. 5, May 1888, p. 193. But we have not in older beds of the Turbiferous or newer beds of the Areniferous Series any suggestion of continuity between the two. There must have been between them an unrepresented period of considerable duration in which very important changes were brought about. Perhaps it was then that England became an island and unsuitable for most of the life of the Areniferous age. Not only have we in the Turbiferous as compared with the Areniferous Series a change of facies but we have many "representative forms," a point to which that keen naturalist, Edward Forbes, always attached great importance. We have for instance in the Fen Beds the Brown Bear (_Ursus arctos_) with his flat pig-like skull, instead of the Grizzly (_Ursus ferox_) of the Gravels with his broad skull and _front bombé_. If we turn to the horned cattle we shall find a confirmation of the view that there was not an entire break between the Turbiferous and Areniferous fauna for the Urus (_Bos primigenius_) occurs in both. This species became extinct in Britain in the Turbiferous period and before the coming of the Romans, for no trace of it seems to have been found with Roman remains in this country; and indeed when we remember the numerous tribes, the dense population and high civilisation of the natives of Britain in Roman times it seems improbable that they can have tolerated such a formidable beast as this wild bull around their cultivated land. Some confusion has arisen as to the description and the names of the Urus and the Bison. Caesar, who was not a big game hunter and probably never saw either, has given under the name Urus a description which evidently mixes up the characters of both. Both existed on the continent down to quite recent times and the Bison is still found in Poland, but later writers also have evidently confounded them. For instance, the Augsburg picture of the Urus is correct, but Herberstein's, which also is said to represent the Urus, is obviously that of a Bison. I have gone into this question more fully elsewhere[7].