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Show 1874.] ON FOSSIL ARVICOLIDiE. 403 mens from Kent's Hole, agreeing closely in character with those from Kirkdale, were not inferior in size to the existing Water-Vole. Dr. Schmerling figures what appears to be the present species from the Belgian bone-caves ('Oss. Foss. des Cavernes de Liege,' 1833). In 1852 M . Pomel described two new species, A. antiquus and A. robustus, from the Breche de Coudes and other French deposits, defining them by slight cranial differences, probably attributable to age, and by the anterior space of the first lower molar being rounded in the first and almost triangular in the second-a variation constantly met with in A. amphibius. In considering the size of fossil Voles allied to the present, it must be remembered that several races now exist in Europe which vary very greatly in this respect, and which are often regarded as distinct species. Of these the best marked are A. amphibius (Linn.), A. terrestris (Linn.), and A. destructor, Savi; and it has been shown by Blasius (Saugeth. Deutschl. pp. 344-358) and by Fatio ('Campagnols du Leman,' pp. 36-48), that although typical examples of each form are very different in size, proportions, and external characters, yet they run into one another by such numerous gradations that it is impossible to find constant characters by which they may be defined and separated. Such being the case with the recent animal, it is, of course, all the more impossible to separate fossils by the teeth and jaws alone. Prof. Owen mentions some portions of upper and lower jaws from " the older Pliocene crag near Norwich," found along with molars of Mastodon angustidens, as indicating a species of Arvicola intermediate in size between A. amphibius and A. agrestis. Sir C. Lyell, in his 'Elements' (5th ed.), figures these teeth, though on too small a scale for satisfactory identification, but remarks that he does not now regard these beds as older Pliocene, believing that some of their fossils, including perhaps the Mastodon, may have been washed out of the Red Crag. Prof. Owen having kindly informed us that the specimens in question had been in the collection of the late Miss Gurney of Northrepps, and were now in the Norfolk and Norwich Museum, we applied, through our friend Mr. Southwell, to the authorities of that institution, who most liberally allowed us every facility for their examination; and Mr. Reeve, the curator, has also obliged us with the loan of specimens from his private cabinet. Those from the Gurney collection are labelled " Ostend;" and Mr. F. W . Harmer kindly informs us that they are doubtless from the preglacial forest-bed series at that place (between Buckton and Hasbro', on the Norfolk coast). Mr. Reeve's examples are a single jaw from the upper bed of crag at Bramerton, and others from the freshwater beds overlying the forest-bed at Runton, near Cromer: Mr. Harmer considers these last of similar age to the Ostend deposits, and the fossils are identical in appearance. The Bramerton jaw (fig. I, a, p. 464) is not inferior in size to ordinary English examples of A. amphibius,-with which it perfectly agrees in dentition. The same remark applies to some teeth from Ostend; but other specimens from that locality (fig. 1, b, p. 464) and from. |