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Show 262 PROF. HUXLEY ON THE CRANIAL AND [Apr. 6, with small frontal sinuses, are so slightly separated from the lower Alopecoids, that it is hard to say whether we have any right to look for a Thooid representative of Otocyon or not. It is quite as reasonable to suppose that Otocyon is the nearest living representative of the primitive type of the Canidae, whence all the rest have been derived, in the first place, by the differentiation of the Thooid from the Alopecoid series, and, in the second, by the occurrence of corresponding series of modifications leading up to the Fox on the one hand and to the Wolf on the other. 11. If this view of the facts is correct, the key to the morphological relations of the whole of the Canidae must lie in the determination of the affinities of Otocyon. The facts hitherto considered primarily appear to me to suggest looking in two directions-in the first place towards the Procyonidse, and in the second towards the Didelphia. In studying the Canidae it is impossible not to be struck by the wonderful persistency of the fundamental patterns of the sectorial teeth and of those wbich follow them. This singular uniformity can hardly be accounted for by adaptation to similar modes of life; for the pattern is as distinctly marked in C.jubatus and C. procyonoides, which live largely upon fruits and roots and never attack large animals, as in any of the more purely carnivorous Canidae. It must therefore be regarded as a morphological fact of fundamental importance, and the best guide to the immediate affinities of this group of animals. Now, in Bassaris we have a procyonine form, the teeth of which are extraordinarily similar to those of C. zerda, if we suppose the little posterior lower molar of the Fennec suppressed. The posterior margin of the bony palate is on a level with the hindermost molar teeth, and therefore does not extend further back than in the ordinary Canidae. There are no frontal sinuses ; and the ethmoid is hio-h. In Mlurus, again, the patterns of the teeth are essentially canine, though inclining in some respects towards the Bears : the frontal sinuses are large, the ethmoid low, and the cranial cavity has a completely Thooid contour. In this genus, as Prof. Flower has pointed out, an alisphenoid canal is present. The small flattened bulla, with its long meatus, is unlike that of the Dogs ; on the other hand, the carotid canal is long, and its posterior aperture opens into a depression common to it and the foramen lacerum posterius. The bony palate extends considerably further back than in any existing canine animal. In Nasua the fourth premolar above is triangular; but a small second inner cusp is beginning to appear behind the large one. In Procyon this cusp has increased so much that the crown of the tooth is quadrangular. In this genus there is a small cingulum on the inner side of the first and second molars, which thus retain a resemblance to those of the Dog. In Nasua, however, it is no longer visible. In both these genera a line joining the inner and outer cusps of the lower sectorial teeth is almost transverse to the axis of the tooth, and the inner cusp is higher than the outer, as in Otocyon. I find the proportional lengths of the teeth in Nasua and Procyon to be as follows:- |