114 THE WANDERINGS OF ANIMALS [CH. 



the tyrants have spread into North America, chiefly 

 as migrants. 



II. Oscines or singing birds ; with the muscles 

 attached to the dorsal and to the ventral edge on 

 either side of the syrinx. The lowest of these birds 

 are the Suboscines, of which the only representatives 

 are the lyre-bird, Menura, and two small kinds of 

 scrub-bird, Atrichornis, in Australia. The rest, half 

 of the species of the whole class, are the Oscines or 

 singing birds proper, which having probably origin- 

 ated in the northern half of the Old World have 

 since attained world-wide distribution. 



MAMMALS. 



The earliest remains of mammals have been 

 found in the Triassic of Carolina, Dromatherium 

 and Microconodon, and of South Africa, Tritylodoti 

 and Theriodesmus ; others have been described from 

 Patagonian Eocene. This is practically all we know 

 of -possible Prototheria or representatives of the 

 earliest stage of mammals, of which the monotremes 

 are supposed to be the sole and much -modified 

 survivals. Of the next stage, the Metatheria, the 

 marsupials are the modernised survivals, or side 

 branch, whilst from the main Metatherian stem has 

 been evolved the last or Eutherian stage, comprising 

 the placental mammals. As to the place of origin 



