CORYPHODON, Ow.—Rarely has the writer felt more misgiving in regard to a conclusion based, in palmontology, on a single tooth or bone, than that to which he arrived after a study of the unique fragment of jaw with one tooth dredged up off the Essex coast, and on which he founded the genus Coryphodon.* The marked contraction of the part of the jaw near one end of the tooth seemed, at first view, clearly to show it to be the narrower fore part of the ramus ; in that case the tooth would have been a premolar, and of comparatively little value in the determination of a genus or species. But a closer in spection showed the line of abrasion of the summits of the two transverse ridges of the tooth to be on one side, and the gene ral law of the relative apposition and reciprocal action of the upper and lower grinders in tapiroid Pachyderms determined that those oblique linear abrasions must be on the hinder side of the ridges. The smaller characters carried conviction against the showing of the larger and more catching ones. So, in determining the position of the nautilus in its pearly abode, when the animal without its shell was first brought to Eng land in 1831, the reasons afforded by some small and incon spicuous parts in like manner outweighed the first impressions from more obvious appearances, as well as the bias from the general analogies of testaceous Univalves. Some contemporary naturalists asserted, and for a time it was believed, that the nautilus had been put upside down in its shell,t just as some contemporary anatomists surmised that the writer had mis taken the fore for the back part of the jaw of his Coryphodon, which, in that case, might only be the known Lophiodon. In both instances the conclusions founded on the less obvious characters have proved to be correct. And the writer would remark that in the course of his experience, he has often found that the prominent appearances which first catch the eye, and indicate a conformable conclusion, are deceptive ; and that the less obtrusive phenomena which require searching out, more frequently, when their full significance is reasoned up to, guide to the right comprehension of the whole. It is as if truth were whispered rather than outspoken by Nature.
Truth, it is sometimes said, lies at the bottom of a well. The first additional glimpse that the writer obtained of the veritable nature of one of our most ancient tertiary Mammals was derived from the inspection of a fossil tooth brought up from a depth of 160 feet, out of the " plastic clay," during the operations of sinking a well in the neighbourhood of Camber well, near London. It was a canine tooth,* belonging, from its size (near 3 inches in length), to a large quadruped, and, from the thickness and shortness of its conical crown, not to a carnivorous but to a hoofed Mammal, most resembling in shape, though not identical with, that of the crown of the canine tooth of some large extinct tapiroid Mammals, which Clavier had referred to his genus Lophiodon, but which has proved to belong to Coryphodon.
The last lower molar of Lophiodon has three lobes ; the molar determined to be the ultimate one, in the fragment of lower jaw above referred to, resembles that of the tapir in the absence of a third or posterior lobe, but the posterior ridge or part of the cingulum is less developed than in the tapir. It presents two divisions in the form of transverse ridges or eminences, the front ridge being the largest, and with its edge most entire. From the outer end of each division a ridge is continued obliquely forward, inward, and downward : the ante rior one extends to the antero-internal angle of the base of the crown ; the posterior one terminates at the middle of the inter space between the two chief divisions of the crown. The trenchant summit of the anterior ridge is slightly concave toward the fore part of the tooth, as in that of Lophiodon ; but its outer and inner ends rise higher, and appear as more dis tinct cones or points ; whence the generic name of Coryphodon. The posterior division is lower than the anterior one, and is bicuspid ; the trenchant margin connecting the outer and inner points does not extend across the crown parallel with the anterior ridge, as in Tapirus and Lophiodon, but bends back so as to form an angle, the apex of which rises into a third point.
Some lophiodontoid fossils from the lignites of Soissons and Laon, and from the plastic clay of Meudon in France, including the upper molar tooth figured by Cuvier in the chapter of the Ossemens Fossiles entitled " Animaux voisins de Tapirs," pl. vii, fig. 6, belong to the genus Coryphodon. Cuvier compares this tooth with one from Bastberg, which he figures in pL vi., fig. 4, and which is certainly the last upper molar of a true Lophiodon, and points out truly that the Soissons tooth differs in the ex ternal border passing into the posterior one, so that, instead of being quadrangular, its crown is triangular ; but he explains this difference on the hypothesis that the Bastberg tooth was a penultimate molar. The reduction of the second or posterior ridge to a semi-circular one, developed at its middle and hind most part into a prominent cone, so far agrees with the modi fication of the same part of the last molar of the lower jaw of the Coryphodon as to render it very probable that the last upper molar from Soissons, figured by Cuvier in pL vii., fig. 6, above quoted, also belongs to the genus Coryphodon. Cuvier states that the entire skeleton was found, indicative of an animal as long and almost as large as a bull ; but that the workmen employed in the sandpit (sabloniire) preserved only that one tooth. Both the lower molar from Harwich, and the upper one from Soissons, indicate an animal of at least double the size of the American tapir.
Professor Hebert * has recently described a very instructive series of teeth and bones from the oldest eocene deposits in France, which he refers to the genus Coryphodon : the last molar is identical in form with the tooth from the plastic clay of Esse; on which the genus was originally founded.