252 Proceedings of the Royal Physical Society. 



Genera — Perichceta (inclncling Megascolex as a sub-genus) ; 

 PerioiiTjx, E. P. ; Diporochmta, F. E. B. ; Anisochcuta, 

 F. E. B.; Hoplochoita, F. E. B.i 



2. Family Cryptodrilidse. 



SeicB 8 in number per segment, ]}aired or distant. Nephridia 

 diffuse or paired — if paired, symmetrical or alternate. 

 Atria tubular or lobate ; penial setoe present or absent. 



Genera — Gryptodrilus^ Fletclier ; Megascolides, M'Coy ; 

 Digaster, E. P. ; Didymog aster, Fletch. ; Dichogaster, 

 F. E. B. ; ? Plutellus, E. P. ; Perissogaster, Fletch. ; 

 Microscolex, Rosa ; Photodrilus, Giard ; Pontodrilus, 

 E. P. ; Rhododrilus, F. E. B. ; Pygmceodrilus, Mich. ; 

 Eudriloides, Mich. ; Callidrilus, Mich. 



3. Family Deinodrilidae. 



Setce 12 in number per segment. Clitellum occupying three 

 segm^ents (xiv.-xvi.); atria two ptairs of tubular glands 

 opening on to xvii. and xix. ; male generative pores on 

 xviii. Penial setce present ; nephridia diffuse. 



Genus — Deinodrilus. 



4. Family AcanthodrilidaB. 



Setce 8 in number per segment, paired or distant. Clitellum 

 occupying 4: to 7 segnnents, xii. (xiii.)-xviii. (xix.); atria 

 and rasa deferentia as in Deinodrilidce. Pe7iictl setce 

 usually present ; nephridia diffuse or p)aired — if paired, 

 regular or alternate. 



Genera — Acanthodrilus^ Trigaster. {Clitellum exception- 

 ally extended.) 



^ These genera, which are very different from those into wliich the family 

 is usually divided, are defined in my paper (Observations upon an American 

 Species of Fcricha'ta, and upon some other Members of tlie Genus — 

 P. Z. S., 1890, pt. ii.) upon this family. Vailiant (Histoire des Anneles, 

 etc, p, 63) divides Perichmta into no less than eight sub-genera, but on the. 

 variations of characters, which I do not agree with him in regarding as very 

 important. Among these are Kinberg's five genera — Nitucris, Amyntas, 

 Phcretima, Lampito, and Ehodopis, which I had hoped had been finally laid 

 to rest. 



2 Michaelsen (Oligochaeten des naturhistorischen Museums in Hamburg 1, 

 JB. Hamb. wiss. Anst., vi. , 1889) has proposed to separate as a distinct 

 genus Benhaviia those Acanthodrili with more than one gizzard with diffuse 

 nephridia and an "incomplete " clitellum extending beyond male pores. It 

 will include Trigaster. In a later paper (Beschreibung der von Herrn Dr F. 

 Stuhlmann ira MUndungsgebiet des Sambesi, etc., id., Bd. vii., 1890) this 



