v] RELATIVE FREQUENCY 85 



one sub-family, that of the Diplocardiinae, is only 

 found here and contains two genera Diplocardia 

 and Zapotecia with quite ten species between them 

 of which only one belongs to the last-named genus. 

 There are no Geoscolecids (except the chiefly aquatic 

 Sparganophiliis) ; this family stops short in the West 

 Indies where their presence has been briefly referred 

 to in considering the worms of South America. The 

 vast majority of the genera enumerated here are 

 only found in the warmer parts of the North American 

 continent. We have therefore in this division of the 

 world some nine genera of which at least one, viz. 

 Diplocardia (and its close ally, hardly perhaps to 

 be separated, Zapotecia), is confined to it, while 

 Trigaster only extends as far south as to the West 

 Indies. 



Europe and northern Asia, of which Europe 

 alone and certain limited tracts of Asia are at all 

 known, contain all the genera of the family Lumbri- 

 cidae which are (according to Michaelsen) Eiseiiiella, 

 Elsenia, Helodrilus, Octolasium, Lumbricus with 

 various sub-genera of Helodrilus, such as Dendro- 

 baena and Allolobophora. Besides these forms, 

 which amount to at least 130 species, we find the 

 genus Hormogaster, with two species, the only genus 

 of the Geoscolecid sub-family Hormogastrinae ; there 

 is also a species apiece of the genera Criodrilus 

 and Sparganophilus (sub-family Criodrilinae). But 



