132 EARTHWORMS AND THEIR ALLIES [ch. 



among the Geoscolecidae and Sjmrganophihis which 

 however is possibly an accidental immigrant. This 

 region is certainly quite clear. Now according to 

 some persons such as Prof. Heilprin the northern 

 part of America should be joined with Europe and 

 Asia to form an Holarctic region ; while by most 

 authors, the separate name of Nearctic is given to 

 the north of the New World. With regard to the 

 terrestrial Oligochaeta it appears to me that this 

 part of the world is possibly to be excluded altogether 

 as possessing no indigenous worms. 



In considering the distribution of the Mammalia 

 Sir Ray Lankester excluded New Zealand from his 

 view as never having possessed any indigenous mam- 

 malian fauna, and termed this part of the world 

 Atheriogaea. In the same way it is possible that the 

 northern part of the United States and Canada, 

 whose earthworm fauna consists of species of Lum- 

 bricidae identical with those of Europe, may possibly 

 be also a region to be excluded in the present survey 

 and spoken of as ' Ascolecogaea.' In the southern 

 part of the United States we shall find genera which 

 will be considered presently. On the other hand it 

 is equally conceivable that this part of the world 

 lost its earthworm fauna through excessive glaciation 

 in the ice age, the forms having been driven south 

 and are now only gradually making their way north- 

 wards again. In this case the modern earthworm 



