134 EARTHWORMS AND THEIR ALLIES [ch. 



the indigeneity of Plutellus. The species according 

 to Dr Eisen show every sign of being genuine in- 

 habitants of California and like certain New Zealand 

 species such as the Tokea esculenfa of Benham 

 (referred by Michaelsen to the genus Megascolides) 

 were eaten by the natives. If these genera were 

 forms restricted to North America, that is not only 

 with reference to the rest of America but to the 

 world generally, there would be as I think no doubt 

 about the pi-acticability of making a Nearctic region. 

 As it is, it seems to me to suit the facts of distribution 

 better to regard the whole of the land under con- 

 sideration as forming one great Neogaean region 

 with three sub-regions, the North American, Central 

 American and West Indian, and tropical South 

 American. This region however will not as I take 

 it include the southernmost extremity of South 

 America. Here in Patagonia and in neighbouring 

 islands we have a different earthworm fauna. It is in 

 fact characterised by the sub-family Acanthodrilinae 

 of which it is true some members of the genus Notio- 

 drilus extend further north. I shall however defer 

 this part of the subject until the more easy delimita- 

 tions of regions are disposed of 



Tropical Africa is evidently to be included in a 

 third region which will be defined by the Eudrilidae, 

 Microchaetinae among the Geoscolecidae, and by the 

 great prevalence of Bichogaster, a genus whose 



