338 ON THE MILK-DKNTITION OF THE KOALA. [Mar. 15, 



Male with an internal subgular vocal sac, and black nuptial ex- 

 crescences on the inner finger. 



From snout to vent 67 millim. 



Three specimens from Faro Island. 



EXPLAJSfATION OF PLATE XXVIII. 



Fig. I. Lepidodacfylus ivoodfordi, p. 334. 



1 a. . Lower view of foot ; multiplied 3 times. 



2. Typhlops aluensis. p. 33(5. Upper view of head ; multiplied 4 times. 



2 a. . Side view of bead ; multiplied 4 times. 



2 6. . Lower yiew of head; multiplied 4 times. 



2 c. ■ . Lower view of tail. 



3. Bafrachylodes vertebralis, p. 337. 



4. Hyla lutca, p. 337. 



4. On the Milk-dentition of the Koala. 

 By Oldfield Thomas. 



[Eeceiyed 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 pre- 

 molar, or pm.^, 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 Eoala, showing milk-dentition ; natural size. 



just such a rudimentary milk-dentition as has been described in the 

 Thylacine by Prof. Flower \ 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. 1S67, p. 63, 



