222 W. B. BENHAM. 



h. Two or more pairs of sperm-sacs ; setse in couples, 

 and exhibiting no tendency to alternate. 



Family VIII. RHiNODRiLiDiE. 

 Genera : — 



24. Rhinodrilus. 



25. Microchaeta. 



26. Urobenus. 



27. Hormogaster. 



28. Bracbydrilus. 



2. Sperraiducal pores in front of Somite xviii, anterior to 

 the clitellum. 



Family IX. Lumbricid^. 

 Genera : — 



29. Lumbricus. 



30. AUolobophora. 



31. Criodrilus. 



32. Allurus. 



III. Characters of the Families and Genera in extenso. 

 Branch I. Plectonephrica. 



The excretory system is in the form of a number of delicate 

 tubules in each somite, more or less united to form a network, 

 and having numerous external apertures in each somite. Added 

 to this, there may be a pair of larger " nephridia," each pos- 

 sessing one external aperture and a funnel communicating 

 with the coelom. 



a. The setae are never more than eight (with the exception of 

 one genus) per somite ; and these may be arranged in couples, or 

 are more or less separated from one another. 



1. Spermiducal pores in Somite xvii or xviii ; only one pair 

 of "prostates," which lies in the same somite as these pores. 



Family I. TypHiEiDyE, mihi (= part Eudrilidae, Rosa). 

 The clitellum, which is more feebly developed on the 

 ventral than on the dorsal surface, begins on Somite xiii or 



