308 W. BLAXLAND BENHAM. 
connected apparently with Pericheta, while its genital and 
alimentary systems are on the Acanthodriloid plan. 
The genus appears to support the view as to a Perichetous 
condition which I have put forward in my recent paper on the 
“‘ Classification of Harthworms” (p. 275), viz. that it is not 
primitive, but secondary, and hence may be developed in any 
family. 
It seems evident, too, that the meganephric and plecto- 
nephric condition may occur within the same genus, as we see 
to be the case in Acanthodrilus, and that this condition of 
the nephridium is not of itself sufficient to decide to which 
series of families a genus belongs. The sum of the characters 
of Plagiocheta places it amongst the Plectonephrica, 
mihi, or Acanthodrilini of Beddard. 
The general features of its internal anatomy point to its 
close affinity with the family Acanthodrilidz, mihi, rather 
than with the Periche tide. 
Beddard forms two families, Deinodrilide and Acan- 
thodrilide, to contain the genera which I have grouped in 
one family. I think that we shall do well to wait awhile before 
we subdivide the families too much; and I would still retain 
Deinodrilus in the same family as Acanthodrilus, Tri- 
gaster, and Benhamia, for it differs from these only in the 
possession of twelve chetz; the extent of clitellum not being 
even a generic distinction, since it varies in different species of 
Acanthodrilus. 
I therefore place Plagiocheta as a fifth genus in the family 
Acanthodrilidx, mihi, with the following characters :— 
The chetz are numerous, and arranged in couples, so as to 
form nearly a complete circle in each somite. The clitellum 
is short. There are four sperm-sacs; the spermathece have 
diverticula; penial chzetz replace the ventral chetz of Somites 
XVII, X1x; a pair of calciferous glands is present. There are 
no peptonephridia ; no dorsal pores. Some of these characters 
are shared by some one or more of the other genera of the 
family. 
It is possible that Bourne’s P. Stuarti may belong to this 
