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Show 776 MR. W. N. PARKER ON THE INDIAN TAPIR. [Dec. 1 9» Tapir, evidently older than the above. This shows exactly the same thing-the last milk-molars still in place and much worn, the corresponding premolars in their sockets in the jaw, and the first true molars above and below in place, the last two (sixth and seventh above, and fifth and sixth below) not having yet come into use. Prof. Flower has shown me a series of Tapir's skulls in the College of Surgeons' Museum, in which the different stages of the first premolar can be seen, up to the time at which it takes its place amongst the others. Comparing the patterns of the milk-teeth with the permanent ones, they, with the exception of the first, are seen to resemble one another very closely. The inner cusp of the first deciduous molar is much larger than in its successor, and thus more nearly resembles the pattern of the other grinders; moreover, both upper and lower first milk-molars are considerably larger than their successors (see Plate LIX. figs. 5-8). The outer incisiors in both jaws are relatively not so large as in the adult, being only about the same size as the inner and middle ones: the canines also are relatively smaller. In the skeleton I have only a few remarks to make on certain parts of the skull and on the pelvis. The tympanic bone, with the external meatus, is small, and does not become ankylosed to the surrounding parts; so that it is rarely seen in dry skulls. Between the tympanic and periotic, on the lower side, is a flat, somewhat curved fibro-cartilage (Plate LIX. fig. 9, ty1), which passes posteriorly into a mass of fibrous tissue, in which is imbedded a very definite os bullae (o.b), similar to those which exist in the Pig1, Bat, &c, except that in these animals there are more than one. The fibro-cartilage is the homologue of that part of the tympanic which, in such mammals as the Carnivora, becomes ossified separately to form the bulla2 ; and the os bullae corresponds roughly to this ossification. In these mammals the tympanic ossifies by two centres, one forming the outer part, and giving rise to the external meatus and to the region which gives attachment to the membrana tympani, and the other forming the bulla. These two parts eventually completely fuse together. Thus in the Tapir, Pig, and Bat only the outer ossification becomes of any physiological importance, the inner one remaining in a rudimentary condition. The stapes is elongated, as in other Ungulates; and there is a distinct interhyal cartilaginous nodule imbedded in the tendon of the stapedius muscle. Above the pterygoid proper there is a separate mesopterygoid centre in the form of a thin scale of bone on each side. This is common in Marsupials, and exists also in the Fox and Pig3. In the pelvis there was a small separate ossification on the upper 1 See W. K. Parker, "On the Structure and Development of the Skull in the Pig," Phil. Trans. 1874. 2 See Prof. Flower, " On the Value of the Characters of the Base of the Cranium in the Classification of the order Carnivora," P.Z.S. 1869, pp. 15-17 a Cf. W . K. Parker, loc. cit. p. 324. |