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Show 1875.] PROF. W. H. FLOWER ON THE MUSK-DEER. 181 out in Milne-Edwards's monograph) by which the Tragulina differ from the Pecora, including Moschus; but perhaps the absence of a distinct ridge on the lower end of the metapodium and the form of the lower jaw may be mentioned as examples-the coronoid process being much less elevated, not rising prominently above the zygoma, and the posterior and inferior surfaces presenting an even curve, without a distinct projection at the angle. It may, in fact, be taken for granted that, when animals of the same original type have been so far modified as to differ in so many important characters as have been shown above, the closer the scrutiny of their structure, the more differences in details will be revealed*. The question of the near affinity of Moschus to the Tragulina being thus eliminated, I will next proceed to consider its position in the group of which it is really a member. The Pecora or true Ruminants form, as has often been remarked, an extremely homogeneous group, one of the best-defined and closely united of any of the Mammalia. But though the original or common type has never been departed from in essentials, variation has been very active among them within certain limits ; and the great difficulty of subdividing them into natural groups (the "despair of zoologists," as Pucheran calls it) arises from the fact that the changes in different organs (feet, skull, frontal appendages, teeth, cutaneous glands, &c.) have proceeded with such apparent irregularity and absence of correlation that the different modifications of these parts are most variously combined in different members of the group. In questions of this kind the absolute certainty of zoological classification referred to above no longer holds, at least in the present state of knowledge, and opinion may be allowed to have sway, and results must be stated with some feeling of doubt aud diffidence. It appears, however, extremely probable that the Pecora very soon branched into two main types, the Cervida and the Bovida (otherwise the antlered and the horned Ruminants), the Giraffe being perhaps an early and since much modified offset of the former-though whether this be the case or whether it be regarded as a third distinct type may be left out of present consideration. Although by the general consent of all naturalists the two main groups thus indicated are held to be distinct, and although there is no difficulty in separating them by the character of their frontal appendages, it is by no means easy to find further characters universally applicable by which they can be distinguished, and which are necessary in the cases in which such appendages are not developed, as in the animal now under discussion. It may be said generally that the Bovida are distinguished from while in the form and greater freedom of the inner metacarpal and metatarsal bones it is further removed from them. In both genera the true molars are much less deeply indented by the enamel inflections, and the characteristic. " Ruminant " crescent less distinctly defined than in the Deer. * Dr. J. Chatin has recently described the muscles of the limbs of Hyomoschus, and finds, as might have been anticipated, that they differ much from those of the Pecora and rather resemble those of the Suina (" Observations sur la Myologie de YHyomoschus," Annales des Sciences Naturelles, 5" serie, t. xv. 1872, p. 1). |