160 EXTINCT POLYPROTODONTS CHAP. VII 
Australia. The most interesting fact in connexion with the 
Tertiary Polyprotodonts is the existence in South America of such 
genera as Prothylacinus and Amphiproviverra, 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 in form; 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 Ificro- 
hiotherium, 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. 
