92 EARTHWORMS AND THEIR ALLIES [ch. 



To find other instances of widely spread genera 

 we must recur to the great family Megascolecidae. 

 There are practically no Geoscolecidae which have 

 a really extensive range. The only instances are 

 Criodrilus and its ally Sparganophilus which occur 

 in America, whether North or South, and in Europe ; 

 but as these forms are at least largely aquatic the 

 facts are not quite comparable with those now under 

 consideration. 



The genus i>^C'/iO</rtste/' (which includes as synonyms 

 Benhamia, Millsonia, Microdrilus) is unquestionably 

 indigenous to tropical Africa and certain parts of 

 America including the West Indies. It has been 

 also met with in the East ; but as the species there 

 occurring, such as for example the species originally 

 described by myself as Microdriltrs saliens, are of 

 small size, an accidental introduction is quite possible, 

 and it is by no means certain that it has not occurred. 

 In any case the genus is known to possess species 

 which are undoubtedly to be reckoned among pere- 

 grine forms such as D. bolavi, which has turned up 

 in Europe. Gordiodrilus and also Ocnerodrilns with 

 its sub-genera have very much the same range as has 

 Dichogaster. It is to be noted however that these 

 forms are circumtropical, and that their distribution 

 is thus less continuous than that of Notiodrilus ; they 

 do not however show the markedly discontinuous 

 range of certain other genera of Megascolecidae. For 



