Professor Schaaffhausen and Dr. Buchner regarded this skull as a race-type, and Professor Huxley has said "that it truly forms only the extreme member of a series leading by slow degrees to the highest and best developed forms of human skulls."[43] That this skull is a race-type is evident from the fact that it is not an isolated case. The fragment of the skull from the loess of the Rhine (Alsace), by its depressed forehead and strongly projecting superciliary arches, greatly resembles the Neanderthal skull. The skull from the calcareous tuff of Constatt, in its low, narrow forehead and strong superciliary arches, resembles the Neanderthal.[44] The cranium found in bone breccia, in Cochrane's Cave (Gibraltar), "resembles, in all essential particulars, including its great thickness, the far-famed Neanderthal skull. Its discovery adds immensely to the scientific value of the Neanderthal specimen, if only as showing that the latter does not represent, as many have hitherto supposed, a mere individual peculiarity, but that it may have been characteristic of a race extending from the Rhine to the Pillars of Hercules."[45] In speaking of the Neanderthal skull, Professor Schaaffhausen says, "It is worthy of notice that a similar, although smaller projection of the superciliary arches has generally been found in the skulls of savage races.... The remarkably small skull from the graves on the island of Moën, examined by Professor Eschricht; the two human skulls, described by Dr. Kutorga, from the government of Minsk (Russia), one of which, especially, shows a great resemblance to the Neanderthal skull; the human skeleton found near Plau, in Mecklenburg, in a very ancient grave, in a squatting position, ... the skull of which indicates a very distant period, when man stood on a very low grade of development;" and other similar discoveries near Mecklenburg, their skulls likewise presenting short, retreating foreheads and projecting eyebrows.[46] Professor Huxley considers that the Borreby skulls, belonging to the stone age of Denmark, "show a great resemblance to the Neanderthal skull, a resemblance which is manifested in the depression of the cranium, the receding forehead, the contracted occiput and the prominent superciliary ridges."[47] _Human Skull of Arno._--The human skull, found by Professor Cocchi in the valley of the Arno, near Florence, in diluvial clay, together with various bones of extinct species of animals, is considered by Carl Vogt to be of like antiquity with the Engis and Neanderthal skulls.[48] CHAPTER IV. PRE-GLACIAL EPOCHS. The age immediately preceding the glacial, and consequently the post-tertiary, is known as the pliocene epoch, the last of the tertiary.