[13] OLIGOCH^TOLOGICAL RESEARCHES. 891 



found no hair-spines at all. Of the forked spines the lower prong is 

 much wider and longer than the upper one, and the angle between the 

 prongs is nearly a right one (Fig. 6 C). 



The length of the worm is about 30™™, and the width less than 1""". 

 The cingulum is small and hardly i^erceptible. 



Habitat. — Sweden, Europe, Motala Eiver, in shallow water near the 

 shore. 



Gen. PSAMMOEYCTES Yejdovsky, 1877. 



Syn. 1868. Scenuris, Kessler, Beitrage zucl. Obhandbuug. d. Petersburger Nat. Forscb. 



Versaml., p. 108. 

 1871. Tubifex, E. Eay Lankaster, Annals & Mag. of Nat. Hist., vol. vii, 1871, 



pp. 90, 101. 

 187.^>. Tubifex, Ed. Perrier, Syr. 1. Tubifex etc. Arch. Zool. exper, et geu. toui. 



iv. No. 1. Notes et Eevue, p. 6, 1875. 

 1877. Psammoryctes, Vejdovsky, Zeitscbr. f. wiss. Zoologie ; Bd. xxvii p. 137. 



From the descriptions of the above authors the following seem to be 

 the main characteristics of the genus : The atrium is furnished with a 

 large globularc hamber called vesicula seminalis, upon which the pros- 

 tate gland is " grafted." That part of the atrium which is situated 

 between this chamber and the penis proper is not glandular, but trans- 

 lucid, narrow, and sometimes furnished with small circular chambers. 



The comb-like spines are fan-shaped, the membrane between the 

 prongs being very plainly visible. 



For further particulars about this genus I beg to refer to the above 

 cited authors. 



Only one species as yet known, viz : 



Psammoryctes umbellifer {Kessler, 1868). 



Syn. 1868. Scenuris umiellifera, Kessler 1. c, p. 108. 



1877. Psammoryctes wnbellifera Vejdovsky 1. c, p. 137. 



Species characteristics the same as for the genus. The spines are 

 of three kinds, viz, hair-spines, comb-like spines,' and common forked 

 spines. Of the latter we find two varieties. 



Sahitat. — Europe, Eussia, Bohemia, England, &c., in fresh or brack- 

 ish water, as it seems very widely distributed. 



Further ahead, when speaking of the general organization of the 

 oviducts and penis sheath, I will return to this species and give some 

 reasons why I think that said organs have been in this as well as in 

 some other species erroneously observed or misunderstood. 



Gen. TUBIFEX Lamark, 1818. 



Nervous system. — The cephalic ganglion emarginated both in front 

 and behind. 



Generative system. — The lower end of the atrium is comparatively 

 broad J not so broad, however, as in Ilyodrilus. Both oviduct and 

 penis sheaths i)resent. The oviduct is wide and short. 



