﻿2 24 Allan's naturalist's library. 



PART TI. 



MONOTREMES— ORDER MONOTREMATA. 



INTRODUCTION. 



At the commencement of the first part of this work it was 

 shown that the Marsupials, or Pouched Mammah, constitute 

 not only a distinct order (Marsupialia) in the Mammalian class, 

 but that they likewise form a separate sub-class variously known 

 as the Didelphia, Metatheria, or Implacentalia, in opposition 

 to the group known as the Monodelphia, Eutheria, or Placen- 

 talia, which contains all the other members of the class save 

 those to be now considered. 



The representatives of this latter group, which are very few 

 in number, and strictly confined to Australia, Tasmania, and 

 New Guinea, are known as Monotremes, or Egg-laying Mam- 

 mals, and agree with the Marsupials in constituting not only a 

 distinct order (Monotremata), but likewise a separate sub- class ; 

 — the sub-class being designated by the name of Ornithodelphia, 

 or Prototheria. So vast mdeed is the difference between these 

 Egg-laying Mammals and all other members of the class to 

 which they belong, and so closely do they connect the latter 

 with the lower classes of the Vertebrate sub-kingdom, that some 

 systematic zoologists do not consider that their separation as a 

 sub-class of equivalent rank with those respectively containing 

 the Pouched and the Placental Mammals, sufficiently emphasizes 



