100 THE MAMMALIA. 



An animal allied to the European Plagiaulax is 

 described by Marsh from the Jura of Wyoming 

 Ctenacodon - - without the above-mentioned deep 

 grooves on the premolars, but they are jagged on 

 the upper edge. 1 In addition to this, in 1883 

 a discovery of great interest was made, by which 

 the connection between the primary and the exist- 

 ing Marsupials has been almost directly restored. 

 In the Lower Eocene, in the neighbourhood of 

 Eheims, Lemoine found the jaw of an animal which 

 shows a remarkably grooved tooth as the only pre- 

 molar, and behind it two low tuberculate molars 

 (Fig. 3, A). Owing to its close resemblance Lemoine 

 called it Neoplagiaidax, and classes it by the side of 

 the existing dwarf-kangaroo of Australia, the Bet- 

 tongia penicillata (Fig. 3, B). This latter also has 

 a grooved tooth, even though somewhat less deeply 

 marked. 



As the Eocene animal has two, and Bettongia 

 three teeth behind the grooved tooth, we cannot, of 

 course, speak of any direct relationship, but we 

 may assume a lateral connection between the two. 



1 We shall here use the words premolars and molars (as most 

 palaeontologists do), although according to the conditions of the 

 living Marsupials, we are not absolutely certain whether we are 

 right in distinguishing the teeth of the fossil forms as milk and 

 permanent teeth, premolars and molars. 



