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Show 276 PROP. HUXLEY ON THE CRANIAL AND [Apr. 6, In none of these skulls was a trace either of the hindermost lower molar or of its alveolus to be seen. Jerdon states that G. primcevus " is common in Ceylon, where it is called the Dhole by some, hy which name it has been treated.of by Hamilton Smith and other writers ; and it is found all over the jungles of Assam, Burmah, and the Malayan peninsula," which is in contradiction to the commonly received opinion that there are no wild dogs in Assam and Burmah. _ According to S. Miiller, the same species is found in Borneo. The distribution of this group over an area which covers nearly 60 degrees of latitude and about as much of longitude in Eastern and Southern Asia is very remarkable, when taken in conjunction with the fact that the proper Jackals, although coexistent with Cyon in Hindostan, are absent over the rest of the Cyon area, except perhaps in Burmah ; while, to the westward of Hindostan, Cyon, so far as is known, is absent in the vast area inhabited by the Jackals. For the species united under Cyon appear to m e to be nothing but lar,ge and slightly modified forms of the Jackal type, which thus seems to have become somewhat specialized at the eastern extremity of its area of distribution. I have already referred to the variability of Canis aureus; and the amount of variation exhibited by that species will become still more apparent by an inspection of the following Table of measurements of the skulls of thirteen specimens of Canis aureus from India. From this it appears that the skull of this species may vary in absolute length 28 per cent., in the length of the palate by nearly 30 per cent., in its width by more than 25 per cent., in the length of the basicranial axis by about 20 per cent., in the length of ^ ^ rather more than 25 per cent., in the length of ^-j about 11 per cent. If the measurements of C. anthus, C. lateralis, C. simensis, and C. mesomelus, given in the same table, are compared with those of C. aureus, it is obvious that the great majority fall into place somewhere in the series of C. aureus; and the only notable difference is in C. simensis, in which there is a remarkable elongation of the palate. But this is exactly that part of the skull which varies most in C. aureus; apd the difference in length between the longest and shortest palate in this species, 19 millims., is exactly the same as that between the longest palate of C. aureus and that"of C. simensis. I do not doubt that a larger number of specimens of G. anthus and of C. simensis would afford a complete series of intermediate forms between them and the Common Jackals. Just as, at the eastern extremity of the Jackal area, the large Cyon-fcrm with specially modified dentition is met with, so at its western extremity, in South Africa, the large Lycaon-iorm, with specially modified fore feet, occurs. In the breadth of the prpeniolar region of the upper jaw, and in a more or less marked convexity of the facial contour, Lycaon strongly reminds one of Cyon; but the dentition is complete, stronger, and more wolf-like, and the edges of the hinder preemolars are more deeply lobed. |
