160 ANIMAL LIFE PAST AND PRESENT. 



the mutual relationships of Mammals and Keptiles 

 have undergone a very considerable change. 



Before proceeding further, it will be necessary that 

 we should become acquainted with the names and 

 external features of these peculiar and aberrant types 

 of mammalian life, which have fortunately been pre- 

 served to us among many other strange forms peculiar 

 to the Australasian region, and have thus enabled us 

 to trace, however imperfectly, the connection which 

 seems once to have existed between Mammals and 

 Eeptiles. The most peculiar in external appearance 

 of these two mammals is the one commonly known as 

 the Duck-bill, and scientifically as the Ornithorhynchus 

 anatinus (Fig. 48). The most striking feature about 

 this strange animal is the presence of the duck-like 

 horny beak ensheathing the mouth, from which the 

 creature takes both its popular and scientific names ; 

 and which, when skins were first brought to Europe, 

 was deemed so extraordinary as to give rise to a sus- 

 picion that the specimens were "made up," after the 

 fashion of the well-known monstrous animals of the 

 Japanese. Peculiar as the beak undoubtedly is, it is 

 not, however, of primary interest, since it is one of 

 those structures already alluded to as acquired features, 

 and is not inherited from very remote antiquity; so 

 that there is no sort of connection between this beak 

 and the beak of a bird, beyond the fact that both are 

 used for the same purpose. The Duck-bill has a total 

 length of about 23 inches, of which 2J are formed by 

 the beak, and five by the tail. The body is covered 



