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THE POPULAR SCIENCE MONTHLY. 



all other members of the kangaroo's order, in that mere cartilages 

 represent those marsupial bones which every other memljcr of the 

 order unquestionably possesses. 



Fig. 16. Tasmanian Wolf {Thalacinus Cynoaphalus). 



The last family of the kangaroo's order consists of the true opos- 

 sum, which (unlike all the animals we have as yet passed in review) 

 inhabits not the Australian region, but America only. 



Tliese creatures vaiy in size from that of the cat to that of the rat. 



They are called Dldelphidm, and agree with the DasynridcB in hav- 

 ing well-developed canine teeth and cutting back teeth (Fig. 17) ; in 



Fig. 17. Tebth of Opossum {Bidelphys). 



having the second and third toes free, and five toes to the fore-foot. 

 But tliey differ in that 



1. Cutting-teeth y (more than in any other animal). 



2. A large opposable great-toe. 



3. A tail, naked (like that of the rat) and prehensile. 



One of them is aquatic in its habits and web-footed. Such are the 

 very varied forms which compose the six families which together make 

 up the kangaroo's order, and such are the relations borne by the kan- 

 garoo's family to the other families of the kangaroo's order. 



But, to obtain a clear conception of the kangaroo, we must not rest 

 content with a knowledge of its order considered by itself. But we 

 must endeavor to learn the relation of its order to the other orders of 

 that highest class of animals to which the kangaroo and we ourselves 

 both belong, namely, the class Mammalia^ which class, with the 



