32 



Note. — In the maps wliich illustrate the migrations of 

 the following species an attemj)t has been made to trace 

 their course by separating and gronping the different move- 

 ments, but it must be understood that this grouping is to a 

 certain extent artificial and is only done for the sake of 

 clearness. These successive immigrations are indicated iu 

 the maps by the following signs ; — 



First immigration thus : — 

 Second ,, ,, (5) 



Third „ „ Qo] 



Fourth „ „ <^ 



Fifth „ „ (29) 



Sixth _,, „ <(jA6y 



