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Show 1885.] ON A TOOTH OF MASTODON LATIDENS. 777 3. Description of a Tooth of Mastodon latidens, Clift, Borneo. By R. LYDEKKER, B.A., &c. [Eeceived August 18, 1885.] (Plate XLVIII.) The specimen forming the subject of the present notice was forwarded from Borneo to the Secretary of this Society by Mr. A. H. Everett, C.M.Z.S., who stated that it was found during the early part of the present year by a Kadayan in the jungle in the vicinity of Bruni, on the north-west coast of Borneo. Owing to the country being in a disturbed state Mr. Everett could not visit the locality to make further inquiries ; but there seems no doubt that the history of the specimen is a true one. The specimen is the crown of the last left upper true molar of a tetralophodont Mastodon, and agrees so closely with Indian teeth of the Siwalik Mastodon latidens, Clift x, that it may be safely referred to that species, although it indicates a very small individual. In mineralogical condition the specimen agrees very closely with many Burmese specimens of the teeth of the same species, although its colour is rather darker than is usually the case. The crown carries five low transverse ridges, and a well-marked hind talon (ta) ; each ridge extends straight across the crown, and the intervening valleys are quite open and uninterrupted by accessory tubercles ; there is a very small quantity of cement at the base of the hinder valleys. Each ridge is divided into an inner and an outer moiety by a longitudinal cleft, which is placed nearest to the outer border of the tooth. The first two ridges are partially worn, and show dentine islets ; the third is very slightly worn, but its enamel is not perforated; while the fourth and filth, together with the talon, are untouched; the third and fourth ridges show that there are four cusps on the inner and two on the outer side of the longitudinal cleft. The inner moieties of the first and second ridges present dentine islets with a very imperfect trefoil shape ; and when more worn the islets of the inner and outer moieties would unite and form transverse bands. On the anterior aspect there is a disk caused by the pressure of an adjacent molar, but the posterior aspect exhibits no such disk ; these features, together with the characteristic shape of the crown and the number of ridges, show that the tooth is the last of the true molar series. Compared with the large series of Indian and Burmese teeth of Mastodon latidens figured by the present writer in the ' Palseontologia Indica' (Mem. Geol. Surv. India2), the present specimen agrees precisely in all general characters. The only other species to which it presents any resemblance is the Indian M. perimensis, of which characteristic teeth are figured in the same work3 ; but it is 1 Trans. Geol. Soc. ser. 2, vol. ii. pt. 3, p. 371 (1828). 2 Ser. 10, vol. i. pis. xxxvii.-xxxix (1880). 3 Vol. i. pis. xl., xiii., and vol. iii. pi. xvi. |