456 wiLHELM michal<:lsen. 



] 9 b. Copulatory walls are prominent at the two segments 

 16-17, indistinct at tlie eighteenth segment, hardly 

 recognisable on the fifteenth segment. Sexual setae 

 0-76-0-96 mm. long, 30-60 /i broad, slightly bent at the 

 distal end, flattened like a sabre, ornamented at the 

 distal end by scattered fine scars. 



Microchsetus parvus n. sp. 



20 a. Copulatory walls at the flat ventral side of the body, no 

 lateral projections in their region. Sexual setae 0"6-l"0 

 mm. long and 32-60 fi thick, bent like an s, provided 

 with a nodulus distal to the middle, ornamented at the 

 distal part by very small, irregular, toothed, transverse 

 ridges arranged in two crossing systems of spirals. 



Microchaetus coUetti Bedd. 



20 b. Copulatory walls on the medial slope of lateral projections 



which occupy segments 17-19 in addition to a part of 

 16 and 20. Sexual setae without nodules. . . 21 



21a. Sexual setae about 0" 75 mm. long and 30 /i thick, nearly 

 straight, bent very slightly only at the distal end, orna- 

 mented at the distal part by longitudinal scars arranged 

 in two crossing spiral lines. Microchaetus gracilis M^■c/l. 



21 i. Sexual setae about I'O mm. long and 40^ thick, nearly 



straight, bent very slightly only at the distal end, orna- 

 mented at the distal part 1)y irregularly scattered 

 scale-like projections. . Microchaetus iva,vi Mich. 



22 a. Setae all ventral in position ; median dorsal distance of 



setae equals al)out two-thirds of the whole circumference 

 of the body. Copulatory walls extend from the nine- 

 teenth to the twenty-first segment, touching each other 

 in the median ventral line. Sexual setae O'68-0"75 mm. 

 long, and at the proximal end about 50 fx thick, quite 

 straight, no external ornamentation 



Microchaetus sulcatus (Kinb.) 

 a. The median ventral distance Ijetween the inner- 

 most ventral seta3 diminishes distinctly towards 

 the copulatory cushions. . f. typicus 



(3. The median ventral distance between the inner- 

 most ventral setae does not distinctly diminish 

 towards the copiilatory cushions. 



var. howickianus n. var. 

 22 b. Outermost pairs of setse in the lateral middle lines, or 

 even above them. Median dorsal distance of setae 

 equals one-half of the whole circumference of the body. 23 



