xm PHYLUM CHORDATA 603 



have been found numerous remains of Diprotodonts belonging to a 

 group represented by a single surviving genus, Ccenolestes. These 

 South American Diprotodonts appear, so far as is known, to have 

 differed from the Australian Diprotodonts in the absence of the 

 characteristic syndactylism of the latter. The remainder of the 

 fossil Marsupials hitherto discovered are of Pleistocene age, 



Fig. 1230.— Kototlieriuin mitclielli. Side view of skull. (After Owen.) 



and have nearly all been found in Australia. The Australian 

 Pleistocene Marsupials are for the most part referable to 

 existing families and even genera, representing both the 

 Diprotodont and the Polyprotodont sections ; but some differ 

 widely from existing forms. One of these, Diprotodon (Fig. 

 1229), was the largest known Marsupial, and reached the 

 dimensions of a Rhinoceros ; it occupies a position intermediate 

 between the Phalangers and the Kangaroos. Unlike the latter, 

 Diprotodon had the limbs of approximately equal size, and 

 adapted for walking : both manus and pes were pentadactyle with 

 very small sub-equal digits. Nototherium (Fig. 1230), somewhat 

 smaller than Diprotodon, but also of large size, seems to connect 

 together Diprotodon, the Wombats, and the Phalangers. Thylacoleo 

 (Fig. 1231) is an extinct genus referable to the Plialanger family, 



