MASTODON.

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is now in the Cabinet of the American Philosophical Society atPhiladelphia . Dr. Hays has refigured the specimen, as a lower jawof the Tetracaulodon, in his Memoir in the Transactions of theSociety for 1831. Why Cuvier should have suppressed the in-structive plate of this lower jaw in his 2nd Edition of the‘ Ossemens Fossiles’ I know not. The Plate 26 in Dr. Hay’sMemoir would indicate that both lower tusks were occasionallyretained in the male Mastodon giganteus as they commonly are inthe male Mastodon angustidens.

227. M. angustidens. —The molar teeth of this extinct EuropaeanMastodon are narrower in proportion to their antero-posterior extent,and their grinding surface is more mammillated and less transverselyridged than in the Mastodon giganteus. As in this species the molarseries, on each side of the upper jaw and probably also of the lower,includes two deciduous teeth which are succeeded by one tooth in avertical direction, and this by four other molars progressively in-creasing in size, and pushing out their predecessors as they advance :the total number of molars developed on each side of the upper jawbeing seven ; the greatest observed number in use, or exposed atthe same time is three on each side ; which is reduced in the oldanimals to one on each side.

The first milk-molar PI. 144, fig. 12, d 1,(1) has an oblongsubquadrilateral transverse section, rounded anteriorly: it is ob-scurely quadricuspid; the two anterior cusps are first blendedtogether by attrition, then the posterior external cusp is worndown into the same surface; the posterior internal cusp remaininglongest distinct. It has two fangs.

The second milk-molar (ib. d 2) (2) is at least three timesas large as the first and supports three pair of cusps, the posteriorones being the largest: and the outer one of the middle pairindicates by its lateral projection the outer side of the tooth: anarrower tuberculate ridge is developed at the anterior and pos-terior margins of the crown. Each pair of cusps is reduced byprogressive attrition to a transverse oval depression, the two ex-terior and posterior cusps being the last to yield. It has two

(1) Kaup, ‘ Ossemens Fossiles de Darmstadt,” Pi. 16, fig. 1, & la, PI. 20, fig. 2.

(2) Ibid. PI. 16, fig. 1, & la, PI. 17, fig. 12, PI. 21, fig. 1.