ECHIDNA WALKING. 



CHAPTER XXXVII 

 EGG-LAYING MAMMALS OR MONOTREMES ORDER MONOTREMATA 



THE Australasian Mammals, known as the duckbill and the echidnas, differ 

 from the other members of the class not only in certain important structural points, 

 but also by their young being hatched from eggs laid by the female parent. In 

 their structural differences, and in their mode of reproduction, they resemble Reptiles, 

 although they agree with other Mammals in that the young, when hatched, are 

 suckled by milk secreted by the mother. Owing to these great differences, the 

 Egg-laying Mammals, or Monotremes, as they are technically termed, constitute 

 not only a distinct order {Monotrematd} in the class, but form a separate subclass 

 known as Prototherians {Prototheria) . Consequently we find that Mammals are 

 divided into three primary groups or subclasses, viz. : 



1. EUTHERIANS, or PLACENTALS, containing the first nine orders. 



2. METATHERIANS or IMPLACENTALS, including the Pouched Mammals. 



3. PROTOTHERIANS, represented only by the Egg-laying Mammals. 



These Egg-laying Mammals have no immediate relationship to Birds, but are 

 closely allied to certain extent orders of Reptiles and Amphibians; and the present 

 representatives of the group are highly-specialized creatures, and thus widely differ- 

 ent from the original ancestral types of the Mammalian class, which we may fairly 

 presume to have once existed as members of the Prototheria. Such ancestral types 

 were doubtless furnished with a full series of teeth of a simple type of structure, and 



(H55) 



