TEEE- WORMS OF GREAT BRITAIN. 293 



Allurus. He lias since added Tetragonurus. The curious point 

 to be noticed is, that thougli Eisen created tlie genus Dendro- 

 hcena, he did not recognize the species which would naturally fall 

 under that generic designation, and hence his perfectly natural 

 and appropriate term lias been quietly ignored. It is my 

 purpose, therefore, to revive the term first introduced by Eisen, 

 and to show which of the species hitherto placed under Lumbricus 

 and Allolohophora must be transferred to the subgenus Ben- 

 drohcena. 



In revising Eisen's genus, however, it will be necessary to 

 extend the characters considerably, since he included therein only 

 one species, and that, till now, a very badly described and little 

 understood worm. His diagnosis * is as follows : — 



Dendrob^na, n. gen. 



Tuhercula ventralia in segmento 14 [=15 Eng. method]. 

 SetcB ubique aequo intervallo distantes, exceptis duabus summis, 



quarum intervallum aliquanto majus est. 

 Lohus cephalicus tres partes segmeuti bucealis occupans. 



Eeferring to this subject, Dr. Benham says f : — " Eisen was 

 the first to subdivide the genus Lumhricus into subgenera, 

 according to the relative amount of dovetailirg of the prostomium 

 into the peristomium. This is accompanied by certain other 

 characters, which have been held sufficient to characterize genera 

 in other cases. So that I have retained his subdivisions Lum- 

 hricus and Allololopliora ; but as his genus DendrolcBna is only 

 distinguished from the latter genus in having all the setae equi- 

 distant, and as all stages occurring in the separation are found 

 in Allolohophora, I agree with Eosa that, we ought not to 

 recognize it." 



Consequently the name has been dropped, and in Beddard's 

 * Classification and Distribution of Earthworms,' 1891, is omitted 

 from notice altogether. The statement of Benham to the effect 

 that every degree of separation of the setse is found in Alloloho- 

 phora is true till we remove the species which properly fall under 

 the genus Dendrolcena, and it is strange that neither Eisen, 



* " Om Skand. Lumbr.," in ffifver. af K. Yeten.-Akad. Forh. 1873, no. 8, 

 p. 53. 



t "An Attempt to Classify Earthworms," in Quart. Journal of Micr. Sci. 

 vol. xxxi. pt. ii. (1890) p. 263. 



23* 



