DENTAL CHARACTERS OF AUSTRALIAN RATS, 



597 



they also seem to have had the same crown pattern, certainly 

 they had not the crown pattern which is distinctive of Oonilurus. 

 The measurements of fragments of their skulls are practically 

 those of the Franklin Island Leporillus ; and it is probably not 

 far from the truth to say that a rat very like the modern insular 



Text-fiivure 10. 



Left lower molar series of Leporillus Jonesi. A. Occlusal surface. 

 B. Alveolar cavities. 



form was a contemporary of Thylacoleo and Thylacinus in the 

 northern parts of South Australia . No traces of living rats were 

 seen at Buckalowie, nor do the guano-miners know of the 

 presence of any in the district. 



NoTOMYS Lesson, 1842. 



The only example of this genus that I have been able to 

 examine is N. cervinus, the specimen coming from Miller's Creek 

 to the west of Lake Eyre. 



The specimen is one which shows very little wearing of the 

 occlusal surfaces of the molars. There is seen the same tendency 

 for the tooth to be received in a depression of the jaw as v/as 

 noted in Leporillus. The root-pattern is also reminiscent of that 

 genvis, for the upper molars 1 and 2 are 3-rooted teeth, the 

 roots being one anterior and two posterior. The third molar, 

 however (in the only specimen examined), showed a single 

 cavity which contained a partially subdivided root. (See text- 

 fig 11.) 

 • The root-formula would therefore be 3. 3. 1. 



The lower molars are all 2-rooted teeth, but there is a well- 

 marked tendency towards reduction of the posterior root of the 

 third molar. The root-formula is 2. 2. 2. 



41* 



