KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 15. N:0 7. 23 



Habitat. Greenland, at Godhavn. 



I forinerly described this species under tlie name of Encliytrcms Pagenstecheri 

 Ratz., but now I have no doubt that the two species differ widely, and resemble each 

 other in external characters only, and in tbe form of the supra-oesophagial ganglion, 

 which however only indicates that they belong to the same subgenus according to the 

 characters ffiven above. 



to* 



10. ArchiencliytraMis nervosus n. sp. 

 Pl. VIII. Fig. 16. 



The supra-oesophagial ganglion is very large and its posterior emargination very 

 deep. The ventral chord shows several large ganglionic swellings not observed in any 

 other species (fig. 16. b). 



The receptacle reseinbles that of the preceding species, but the tube is conside- 

 rably shorter than the receptacle proper, and is moreover furnished with glands only at 

 the base (fig. 16. c). 



The vesicle of the efferent duct is long and narrow, sometimes bent near the 

 top. The penis is large and hooklike in perfectly developed specimens (fig. 16, f). 



The segmental organs and the perigastric cells are not known. 



The testes and the ovaries are very large and lobed. 



The spines are all of equal length and curved, in each fascicle about 4. 5. 6. 4. 



The length of the body about 15 m. m. 



The width of the same about 1 m. m. 



Habitat. Of this species only two individuals were fonnd among numerous speci- 

 mens of N. Stuxbergii collected at the North Gusinnoj Cape of Novaja Semlia at 72° 10' 

 lat. Through a very unlucky mishap both specimens were destroyed before any fur- 

 ther investigation was made. 



The size and shape of the cerebral ganglion, the receptacle, and the large swell- 

 ings of the ventral ganglion distinguish this species from any other known to me. The 

 size and the colour of the body is exactly like that of N. Stuxbergii, the only external 

 differences are the more defined segments and a different shaped headlobe. It is pecu- 

 liar that the receptacle to such great extent resembles that of the species along with 

 which it was found. To judge from certain seaweeds found among the specimens 

 it is likely that they had been living under decaying seaweeds on the shore, perhaps 

 below the tide mark. In that case they, as well as A. profugus and N~- Stuxbergii, 

 should belong to Clapakédes genus Pachydrilus. 



The great resemblance of the receptacles of the said species may perhaps be explai- 

 ned by their similar way of living, as it is by no means unlikely that similar external 

 conditions may be corresponding with similar internal changes even in the organs of 

 generation, especially when the ways of fertilization etc. must necessarily be irifluenced 

 by the worin being surrounded by water or not. 



