16 GUSTAF E1SEN, ON THE ARCTIC OLIGOOH^TA. 



a. The interiör tube of the segmental organs is nearly half as wide as the big 

 lobe ... A. g emmatus. 



b. The interiör tube of the segmental organs is very narrow and diverging from 

 the big lobe ... A. ochraceus. 



c. The interiör tube of the segmental organs is narrow but pressed to the 

 big lobe. 



1. The supraoesophagial ganglion is broader than long ... A. nasutus. 



2. The supraoesophagial ganglion is longer than broad, or as long as broad . . . 



A. affinis. 



C. The receptacle is rather short but at the top furnished with a very large 

 oval vesicle or receptacle proper. 



C". The tube is shorter than the receptacle proper, and furnished with nume- 

 rous glancls at the base ... A. nervosus. 



C". The tube is longer than the receptacle proper and covered all along with 

 numerous glands ... A. profugus. 



1. Archienchytneus LeYinsemi n. 

 Pl. III. Fig. 4. 



The supra-cesophagial ganglion is eonsiderably broader behind and its posterior 

 margin is deeply concave (tig. 4. e). 



The receptacle consists of a long simple tube about 14 times longer than wide. 

 The actual length of the receptacle is the same as that of the following species, A. 

 tenellus (fig. 4. f). 



The vesicle of the efferent duct is simple, neither twisted nor bent. The penis 

 is very large, nearly of the size of the vesicle (fig. 4. g). 



No perigastric bodies. 



The inner tube of the segmental organs is very short or about of Vs the length 

 of the middle lobe. The outer tube on the contrary is of the same length as the said 

 lobe, but much narrower (Fig. 27). 



The testes in the 10 th segments, very small and narrow. 



The ovaries in the ll th and 12 th segments. 



The segments about 50 well separated. 



The length of the body about 8 in. m. 



The width of the same about x /s m - m - 



The spines 6, 7, 7, 6. 



The colour påle whitish or milky. 



Habitat. Found by the expedition in the south of Siberia between the towns 

 Tomsk and Krasnojarsk. 



From the following species A. Levinsenii is very well distinguished bj' the size of the 

 receptacle, the size of the organs of copulation, the absence of perigastric bodies, and 



