456 



OLIGOCHAETA 



It will be obvious from the above table that Photodrilus and Pontodrilus are 

 nearer to each other than either of them is to Microscolex. So near does this 

 resemblance appear to me to be, that I think it is desirable to unite the two genera 

 into one, which must obviously bear the name of Pontodrilus. The only point of 

 importance which divides this genus from Microscolex is the position in the latter 

 of the male pores upon the seventeenth instead of the eighteenth segment. The 

 nearly invariable presence in Microscolex of penial setae distinguishes it from the 

 two remaining forms, which I unite here into a single genus. 



In the following table the principal characters of the genera of Cryptodrilidae 

 are placed side by side for comparison: — 



