320 OLIGOCHAETA 



referred to in the definition. It is also remarkable in having more setae than any 

 other Enchytraeid. MICHAELSEN does not mention the comparative lengths of the 

 sperm-duct and the funnel which is often, apparently, a useful specific character. The 

 clitellum is longer in extent than in any other Enchytraeid ; it reaches from the 

 eleventh to the fourteenth segment, occupying, however, but half of the first and the 

 last of these segments. The egg-sac is single and extends below the gut to the 

 eighteenth segment ; the sperm-sacs are paired and do not extend beyond the fourteenth 

 segment. The lymph corpuscles are flat and Navicella-Yike in form. 



(9) Mesenchytraeus armatus (LEVINSEN). 



Analycus armatus, LEVINSEN, Vid. Med. 1883, p. 232 ] . 



Mesenchytraeus armatus, MICHAELSEN, Abh. Nat. Ver. Hamb. 1889, p. 18. 



Definition. Setae, 1-6 in a bundle, those of segments IV VI (one or two to each segment^] 

 double the length of the rest. Hob. Denmark. 



This species agrees with the last in the possession of large setae ; it is to be 

 distinguished from it by its smaller size, and also in the smaller number of setae 

 in some of the segments. 



Genus STERCTTTTTS, MICHAELSEN. 



DEFINITION. Setae as in Pachydrilus. Head-pores present. Dorsal vessel ante- 

 clitellian in origin, with cardiac body; blood colourless. No salivary glands. 

 Spermathecae not opening into gut. 



This genus, of which our knowledge is entirely due to MICHAELSEN, is in many 

 respects remarkable. It appears to connect the genera Mesenchytraeus and Buchholzia ; 

 it has the cardiac body of the former genus, and the ante-clitellian origin of the 

 dorsal vessel found in the latter. The other characters of the worm I shall regard 

 as specific, and describe under the species 



Stercutus niveus, MICHAELSEN. 



Stercutus niveus, MICHAELSEN, Arch. Mikr. Anat. 1888, p. 483. 



Definition. Length 6 mm. ; numler of segments 28 ; setae 3-4 per bundle. Funnel of 

 sperm-duct small ; spermathecae oval, with no constriction between pouch and, duct ; 

 glands at base of latter. Hab. Germany. 



1 See footnote, p. 317. 



