MARSUPIALIA 



495 



(' inflected ') to form a horizontal shelf (Fig. 388). The lacrimal 

 bone is exposed on the face, with its foramen on the edge of or 

 outside the orbit, and the jugal takes part in the articulation of 

 the jaw. There is a cloaca, and in most forms not only the uterus 

 but the vaginae of the two sides are separate, and to match these 

 the penis, which hangs behind the scrotum, is bifid. The marsupials 



i> m^ m^ m"- 



Fig. 387.— Skulls of a thylacine (above) and of a rat kangaroo (below) .—From 

 Young, The Life of Vertebrates, 1950. Clarendon Press, Oxford. After Flower 

 and Lyddeker. 



c, Canine ; t.. incisor ; m., molar ; pm., premolar. 



are now, except for a few American species, confined to Australasia, 

 and there, away from the competition of the placentals, they have 

 radiated in a number of directions which parallel many of the 

 eutherian orders. Thus Dasyiirus and Thylacinus are carnivorous 

 and have dentition much like a dog's ; the kangaroos {Macroptis) 

 are herbivorous, with lophodont molars, and others are arboreal, 

 rat-Hke and fossorial. There are no truly flying or aquatic 

 marsupials, but Chironectes lives in rivers and other genera 



