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Show 152 PROF. W. H. FLOWER ON THE ELEPHANT SEAL. [Jan. 4, The molars are reduced to the extreme of simplicity (see figs. 1 and 2, pp. 150, 151). Each has a single long, tapering root, shaped somewhat like a carrot, having a thickened shoulder near the neck, caused by the deposition of cementum, and which projects above the alveolus in old animals. The root of the first upper molar is the longest, measuring in the large skull as much as 60 millims. Each of the others is shorter than the one in front of it, to the last, which is not unfrequently rudimentary or absent. In the present case there is no trace even of a socket, on the left side; though on the right side there is a small shallow cavity, from which a tooth appears to have been lost (fig. 1, * ) . In the lower jaw the roots are more equal, that of the first being slightly the longest, and the fifth nearly as large as any of the others. This, however, is absent, as well as that of the upper jaw in No. 2921, which has thus ^ teeth of the molar series, all premolars, according to what is now known of their homologies. The crowns, when young, present traces only of the division into pointed cusps or lobes, so characteristic of the molars of most Seals- mere grooves upon the surface, becoming deeper towards the apex, to which they converge, and marking off rudimentary cusps, more distinct on the outer than the inner surface of the tooth. The fifth molar in both upper and lower jaws is of more simple character than the others, often only a simple cone. In animals soon after birth these teeth are crowded together, the first being placed in contact with the canine. In this stage the teeth consist of little more than the crowns, the incisors and molars being all equally developed and in their places, and the canines with their apices only appearing above the level of the alveolus; the roots are only commencing to calcify ; but as they grow in length and width, not only does each require more room, but they become separated from one another by intervals, which are most extended in the oldest individuals. The five molars of a very young male (No. 3934 A ) occupy a space from before backwards of 44 millims. In the largest skull (3921 A ) the same teeth are spread over 116 millims. In an old skull in the Leiden Museum (of which, the hinder part being broken away, 1 am not able to give the length) not only the whole of the crowns, but even the necks, of all the molar teeth, except the last upper one, have been worn away, and what appear at first sight to be the crowns are merely rounded stumps of dentine and cementum, of very much larger size than the real crowns of the teeth of the young animal. The sexes even of the youngest specimens can be recognized by the comparatively small sizes of the crowns of the canines in the females. In the males there is some difference in this respect, as the following figures (measurements in millimetres) show, though the variations are comprised within certain limits :- |