82 



Vertebratd. 



the opossums have the pouch rudimental, and the 

 mother carries her young ones on her back, often 



with their prehensile tails coiled round her 

 tail. Others, like the yapock of South 

 America, are amphibious, and have webbed 

 feet. 



The kangaroos proper (fig. 38) are 

 characterised by the enormous dispropor- 

 tion of the fore and hind limbs ; the former 

 are short, five-fingered, while the latter 

 are very long with long feet, the middle or 

 third toe (which corresponds to our fourth, 

 as they have no great toe) being enormous 

 in length, the fourth being a little smaller, 

 while the first and second are united and excessively 



