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Show 264 PROF. HUXLEY ON THE CRANIAL AND [Apr. 6, Didelphia and Ornithodelphia \ and other indications of the approximation of the lower Carnivores to the Didelphia are not wanting. If the mandibles of Otocyon, of Procyon, and of Perameles are viewed from behind (fig. 14, p. 263), it will be seen that the angular process is as distinctly inflected in the two former as in the latter, and that the difference in the angular process of Thylacinus is merely one of the degree of development of a homologous and similarly formed part2. I look upon the four molars of Otocyon as another character of the same order ; as a survival, in fact, of a condition of the dentition exhibited by the common ancestors of the existing Canidae and the existing carnivorous marsupials. 12. The geographical distribution of the Canidae presents many points of interest when it is considered in relation to the morphological characters of the forms at present restricted to certain areas of the earth's surface. Otocyon occurs only in South Africa, and apparently does not range beyond the southern extremity of that continent. The microdont Alopecoids with lobate jaws (C. cinereo-argentatus and C. littoralis), which have been separated by Baird under the name of XJrocyon, appear to me to be the nearest existing allies of Otocyon. But there is no representative of this group outside the North- American continent, G. einereo-argentatus occupying the central States of North America, while C. littoralis occurs on the N.W. in California, and on the south as far as Honduras and Costa Rica. Baird suggests that G. littoralis is merely a local race of C. einereo-argentalus; and the measurements in Table XII., which show that No. II. is as near to No. III. as to No. I., lend strong support to this view. The small Foxes of the Old World, G. zerda and G. caama, differ from the foregoing in little more than the uonlobation of the mandible and the less prominent or cord-like character of the temporal ridges. In G. bengalensis, C. corsac, and G. velox the sagittal area narrows and the temporal ridges unite behind, while the sectorial teeth increase in proportional size, and thus gradually lead to the most specialized Foxes of the Old World. This is shown very clearly by the following table of measurements of thirteen specimens belonging to twelve species of Alopecoids. 1 Proceedings of the Royal Society, 1879. I have recently found the epipubis very well developed in a female Bengal Fox and in a female C. mesomelas. My friend Dr. Rolleston, F.R.S., lias been good enough to compare Thylacinus with the domestic Dog; and he informs m e that "the bone is disproportionately small in the marsupial in question; but it has precisely the same relation to the external oblique's bifid tendon, to the rectus and pyramidalis (which are only imperfeetly differentiated from one another and from the inner or upper division of the tendon of the external oblique), and, finally, to the pectineus, which it has in the placental mammal." 2 A comparison of the mandible oi Bidelphys with that of Nasua is even more instructive. In Centetes the angular process is slightly but characteristically inflected. |