220 W. B. BENHAM. 



in each somite, uniting to form a network, with more or less 

 numerous external apertures : a large " uephridium,^' with 

 coelomic funnel, may be present in addition to these tubules. 

 a. Setae, eight per somite (rarely twelve), either in couples 

 or separate. 



1. Spermiducal pores on Somite xvii or xviii; one pair 

 of prostates in the same somite. 



Family I. Typh^idjE. 



Genera : — 



1. Typhseus. 



2. Megascolides. 



3. Cryptodrilus. 



4. Didymogaster. 



5. Perissogaster. 



6. Dichogaster. 



7. Digaster. 



2. Spermiducal pores on Somite xviii ; two pairs of pro- 

 states in Somites xvii and xix. 



Family II. AcANTHODRILIDiE. 



Genera : — 



8. Acanthodrilus. 



9. Trigaster. 

 10. Deinodrilus. 



h. Setae more than twelve, usually twenty to eighty per 

 somite ; arranged in a continuous or discontinuous 

 circle. 



Family III. Perich^etidjE. 

 Genus 11. Perichseta (including Megascolex). 



Branch II. Meganephrica.^ 

 Excretory network absent ; replaced by a pair (rarely two 

 pairs) of large nephridia in each somite. 

 ' M«yac = large. 



