160 EXTINCT POLYPROTODONTS CHAE- vn 



Australia. The most interesting fact in connexion with the 

 Tertiary Polyprotodonts is the existence in South America of such 

 genera as Prothylacinus and Amphipromverra, which are not 

 merely Polyprotodonts but definitely Dasyures, and not referable 

 to the Didelphyidae. 



These forms have been included in an order, SPARASSODONTA. 

 But it is not by any means certain whether these forms are 

 rightly placed in the neighbourhood of the carnivorous Marsupials ; 

 it is possible that they ought to be relegated to the Creodonta or 

 to their allies. Their structure is in fact somewhat intermediate 

 between those two groups. The teeth seem to be carnivorous and 

 Marsupial -like inform; but as already mentioned, in connexion 

 with the general structure of teeth, more than a single premolar 

 is replaced. These animals in fact, in so far as regards their 

 teeth, are midway between the Marsupials and the typical Eutheria. 

 The angle of the lower jaw is inflected, but the palate is not 

 marked by deficient ossification. At least this is not the case 

 with all the members of the group. Whether the small Micro- 

 biotherium, which is made the type of a family, is rightly referred 

 here is not certain. This animal had palatine vacuities as well 

 as an inflected angle to the lower jaw. 



