DENTAL CHARACTEES OF AUSTRALIAN RATS. 



589' 



they were certainly ancient and they were mixed with the remains- 

 of many other animals, amongst which were TJiylacimis and 

 Thijlacoleo. Even the accident of the loss of teeth in the jaw 

 fi-agments composing the deposit on the floor of the caves provided 

 a partial answer to the question, for it was at once evident from 

 an examination of the alveolar cavities for the upper molars that 

 two quite different root-patterns were represented. 



In order to determine the affinities of these root-patterns the 

 author extracted teeth from such properly identified skulls as he 

 could obtain, and the present paper is merely a record of the 

 findings. If the results are capable of no further extension, at 

 least they permit one to say that the past and present rats of 



Text-figure 2. 



<1 B 



Typical fragments from bone debris of Buckalovvie Cave deposit. A. Portion 

 bearing left upper molar root-cavities. B. Left lower molar root-cavities. 



Franklin Island are the same animal, that the murine contem- 

 porary of Thylacoleo which formed the cave-deposit at Buckalowie, 

 was a creature a good deal like the Franklin Island rat ; but that 

 the unknown rat which lives on Goat Island is not the same sort 

 of rat at all, but is like a rat whose remains make a small and 

 recent addition to the cave-deposits and like existing members of 

 the genus Rattus. 



Hydromys Geofi'., 1805. 

 The species examined is that known as the " Golden-bellied 

 Water-Rat, " H. chrysogaster Geofi". It is now a comparatively 

 rare animal, and in South Australia (and in some of the other 

 States) it is becoming increasingly difficult to obtain. The speci- 

 mens examined were trapped either on the Onkaparinga River in 

 the Mount Lofty Range or on the River Murray at Tailem Bend. 

 The animal is so thoroughly distinctive that its specific diagnosis 

 needs no authority. ' 



