238 POUCHED MAMMALS. 



Placental Mammals, thus showing that these islands have had some connection 

 with those of the Malayan region. The channel separating Lombok and Celebes 

 from Java and Borneo is, however, of much greater depth than those dividing the 

 other islands ; and it may accordingly be inferred that any land- connection which 

 formerly existed between the two groups must have been remote. 



In the Tertiary period opossums were distributed over a large portion of 

 Europe ; and recent discoveries indicate the existence during the same epoch of 

 marsupials allied to the Australian thylacine in South America. In the preceding 

 Secondary period, as we shall show later on, Pouched Marsupials appear to have 

 ranged over the whole world, and were then, together with Egg-laying Mammals, 

 the chief, if not the sole representatives of the class. 



THE KANGAROOS AND THEIR ALLIES. 

 Family MACEOPODIDJE. 



We commence our survey of the Pouched Mammals with their most aberrant 

 and specialised representatives, or those commonly known as kangaroos, wallabies, 



rat -kangaroos, etc. And it may 

 be mentioned here, that whereas 

 kangaroos are very frequently 

 spoken of as typical Marsupials, 

 this is really very far from being 

 the case. It is true that they con- 

 form in all essential characteristics 

 to the Marsupial type of structure ; 

 but they have been specially 

 modified for a particular kind 

 of progression namely, leaping. 

 This has profoundly modified their 

 whole organisation, and rendered 

 them some of the most specialised 

 of all Mammals ; and they retain 

 accordingly but little resemblance 

 to what may be termed a typical, 

 or generalised marsupial, such as 

 a bandicoot, or thylacine. 



The kangaroos belong to a 

 group or suborder of Marsupials 

 characterised by the adaptation of 

 their teeth to a vegetable diet. 

 Thus the front, or incisor teeth, 

 as shown in the figure on p. 239, 

 are never more than three in 

 number on each side of the jaws, and are usually three in the upper and one in 

 the lower jaw ; while in all cases the innermost pair in each jaw are of large size, 



SKELETON OF KANGAROO. 



