Zoological Notes. 101 



XIIL Zoological Notes. By Frank E. Bkddai^d, Esq., M.A., 

 F.RS.E., F.Z.S., Prosector to the Zoological Society 

 of London, Lecturer on Biology at Guy's Hospital. 

 [Plate \.'\ 



(Read 17th April 1889.) 

 I. 



On some British Species of Pachydrilus (PI. V.). 



During the month of August 1888, I visited the Marine 

 Biological Laboratory at Plymouth, and occupied myself 

 with the study of the Oligochseta. I have already con- 

 tributed to the Journal of tlie Marine Biological Association 

 a short notice of such Oligochseta as I was able to find, and 

 have published in the last number of the Proceedings of the 

 Zoologiccd Society of London an account of the anatomy of 

 Clitellio arenarius and Hemituhifex henedii, which are the 

 two most prevalent species of Tubificidse on the shores of the 

 Sound. Besides these two species, I met with the genus 

 Paclujdrilus, which is very abundant among coarse gravel at 

 Eum Bay. My study of the material which was obtained 

 from that locality, leads me to believe that there are at any 

 rate two species, upon which I propose to offer some notes 

 to the Society in the present communication. 



The genus Pachydrilus was distinguished by Claparede 

 (1*), by whom it was found on the shores of Holy Island in 

 the Firth of Clyde and the neighbourhood. He described 

 five species, viz., P. verrucosus, P. crassus, P. semifuscus, P. 

 lacteus, and P. ehudensis. Of these species, P. lacteus is 

 probably to be withdrawn from the genus altogether, as it 

 differs from the rest (and agrees with Enchytrceus) in having 

 colourless blood. The red or yellow coloured blood of Pachy- 

 drilus is one of the principal distinguishing features of the 

 genus which mark it out from other Enchytrseidce. Yejdovsky 

 has expressed the opinion that P. verrucosus may be identical 

 with Ratzel's Enchytrceus pagenstecheri. The remaining species 

 have never to my knowledge been reinvestigated. 



* The numbers refer to the list of Memoirs cited on p. 105. 



