DESCRIPTIONS OF GENERA AND SPECIES 325 



CLAPAPEDE'S P. krohnii is incidentally described in his memoir upon the anatomy of Lumbrieua 

 (1, p. 571, footnote) ; this worm, was found in the soil near Kreuznach. It is 5-9 mm. long, and consists 

 of about fifty segments. But CLAPAREDE gives no other characters that are of any use in differentiating 

 the species ; it is hardly necessary to point out that the above are insufficient for this purpose. 



CZEBNIAVSKY has described the following species of ' Pachydrilus ' :~ P. gracilis, P. proximvs, 

 P. affinis, P. similis, P. lacustris, P. charkotnensis, and P. opacus. These are allowed by VAILLANT, who, 

 however, doe's not regard the descriptions as sufficient a conclusion which most will share with him. 

 All these species, together with P. cavicola (JOSEPH), are placed by MICHAELSEN at the end of his 

 Revision of the Enchytraeidae as 'species inquirendae.' 



The well-characterized forms can be divided into two sets according to whether 

 the spermatheca has or lias not a duct distinct from the pouch. 

 The following table will serve to discriminate the species : 



A. Spermatheca without a duct distinct from the pouch. 



(1) Copulatory glands present. 



(a) nearly covering nerve-chord P. lineatus. 



(b) not covering nerve-chord P. litoreus. 



(2) No such structures. 



(a) Setae, 3-5 per bundle P. verrucosus. 



(6) Setae, 5-8 per bundle P. subterraneus. 



B. Spermathecae with a distinct duct marked oft' from pouch. 



(1) Copulatory glands present. 



i. Setae more numerous in ventral bundles . . P. pagenstecheri. 

 ii. Setae equal in both bundles. 



(a) Copulatory glands lobed P. nervosus. 



(b) Copulatory glands not lobed P. maximus. 



(2) No copulatory glands. 



i. Setae not more than 9 in a bundle .... P. profugus. 

 ii. Setae as many as 14 in a bundle P. minutus. 



(i) Pachydrilus nervosus, EISEN. 



Archienchytraeus nervosus, EISEN, Ofv. Svensk. Akad. 1878, No. 3, p. 73. 

 Enchytraeus nervosus, VEJDOVSKY, Syst. u. Morph. 1884, p. 41. 

 Enchytraeus (Archienchytraeus) nervosus, VAILLANT, AnneleX p. 286. 

 Pachydrilus nervosus, MICHAELSEN, JB. Wiss. Anst. Hamb. 1888, p. 58. 



Definition. Length., i$mm.; setae, 4-7 per bundle. Brain concave in front ; outgrowl.hu of 

 nerve-chord large and lobed. Spermatkecae with distinct demarcation between pouch and 

 duct. Had. Nova Zemlla. 



