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Show 338 ON T H E MILK-DENTITION O F T H E KOALA. [Mar. 15, Male with an internal subgular vocal sac, and black nuptial on the inner finger. From snout to vent 67 millim. Three specimens from Faro Island. EXPLANATION OF PLATE XXVIII. Fig. 1. Lepidodactylus woodfordi, p. 334. 1 a. • • -. Lower view of foot; multiplied 3 times. 2. Typhlops aluensis, p. 336. Upper view of head; multiplied 4 times. 2 a. . Side view of head; multiplied 4 times. 2 b. . Lower view of head; multiplied 4 times. 2 c. . Lower view of tail. 3. Batrachylodes vertebralis, p. 337. 4. Hyla lutea, p. 337. 4. On the Milk-dentition of the Koala. By OLDFIELD THOMAS. [Received February 15, 1887.] Among the few remaining Marsupials in which no trace of a milk-dentition has yet been found, the Koala (Phascolarctos cinereus) occupies a prominent place, especially as in this animal the last premolar, or pm.4, which among Marsupials is the only tooth that ever has a milk predecessor, is unusually large and powerful, and might have been therefore expected, as in the allied Phalangers, to have a proportionally well-developed predecessor. At last, however, I have been able to find traces in the Koala of Head of young Koala, showing milk-dentition ; natural size. just such a rudimentary milk-dentition as has been described Thylacine by Prof. Flower1, and showing, just as in that animal, that the ancestors of the Koala have had, and that it has now lost, the ordinary amount of tooth-change found in the great majority of Marsupials. In two very young and hairless Koalas, four and five inches long respectively, I find, on cutting open the side of the jaw, clear and 1 Phil. Trans. 1867, p. 63. |
