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Show 6 PROF. FLOWER ON THE SKULL OF A XIPHODON. [Jan. 4, posterior root. Unfortunately the region in which the posterior of these teeth is situated is most damaged, and its form cannot be clearly made out; but, judging from the analogy of Ceenotherium, Xiphodon, and allied forms, we have here the whole premolar series, the last having two external, and one internal root, obliterated in the specimen, and each of the others two roots only. The canines would thus be the teeth next beyond the line of fracture ; but they evidently could not have been large, or deeply implanted, as in Tragulidae. Of the incisors, nothing can be said from actual knowledge; but all analogies of allied forms lead to the supposition that the complete number (three on each side) were present. It is evident that the animal to which this cranium belonged was a member of that group of Artiodactyles in which the general form of the modern Ruminants was shadowed out, but in which the typical number of teeth (eleven on each side, above and below, in continuous series) was still maintained, a group largely represented in the North-American Miocene strata by Oreodon and its allies, and of which the elegant little Ceenotherium' is one of the best-known European forms. It differs, however, considerably in general form and proportions from any of the former as figured by Leidy, especially in the absence of a suborbital fossa, and is readily distinguished from the latter by the want of the deep median notch in the hinder edge of the palate, and by the more compressed form of the premolars, as estimated by the size of the roots. I am unable, however, to point out any character by which to separate it from Cuvier's Xiphodon, constituted in the ' Ossemens fossiles ' as a subgenus of Anop-lotherium. From the type of that form, X. gracilis of the Paris Upper Eocene, it differs, as far as can be inferred from descriptions and figures, chiefly in superior size, being about one third larger. Another form to which it is closely allied is known as a British fossil from the Upper Eocene of Hordwell Cliff, having been described by Professor Owen under the name of Dichodon cuspi-datus*. This animal is known by the teeth alone ; and it is singular that, as far as the comparison of the size and shape of the roots or alveolar walls will allow, there is no reason why the teeth of Dichodon cuspi-datus should not have belonged to our present specimen. Although there is not yet evidence enough to be assured of their identity, and more perfect specimens of either may show that the idea is fallacious, I yet think it necessary to point out the possibility. But then there are grave doubts, as already expressed by Gervais f, whether Dichodon is really separable generically from Xiphodon. The main character on which the genus was founded, the peculiarity of the last lower premolar tooth, was, as the original describer himself subsequently pointed out, simply the result of a milk-tooth having been mistaken for a permanent one J. The British species attributed to the * Quarterly Journal of the Geological Society, vol. iv. 1848, p. 36. t Zoologie ct Paleontologie Francaise, 2 m e edit. (1859), p. 159. { Quarterly Journ. Geol. Soc. vol. xiii. (1857), p. 190. |