XIII 



PHYLUM CHORDATA 



479 



the inner side of the hind foot, larger in the male than in the 

 female. The tail is vestigial. 



The Opossums (DidelpJiyidw, Fig. 1118) are arboreal rat-like 

 Marsupials, with elongated naked muzzle, with well-developed, 



FIG. 1116. Duck -Bill (Ornithorhynchus anatinus). (After Vogt and Specht.) 



though nailless, opposable hallux, and elongated prehensile tail. 

 A marsupium is sometimes present, but is absent or incomplete 

 in the majority. One species the Water Opossum has the toes 

 webbed. The Dasyurida3 (Australian Native Cats, Tasmanian 

 Devil, Thylacine, &c.) often have the pollex rudimentary, the foot 



warn 



FIG. 1117. Spiny Ant-eater (Echidna aculeata). (After Vogt and Specht.) 



four- toed, the hallux, when present, small and clawless, and the tail 

 aon-prehensile. There is a well-developed marsupium. The Native 

 Cats (Fig. 1119) and their near allies are cat-like animals, the largest 

 equal in size to a Domestic Cat, some no larger than Rats or Mice ; 



