THE OLIGOGH.'ETA OF NATAL AND ZULULAND. 451 



13 a. A pair of large setal papilte on the twelfth segment. 



Microchsetus gracilis Mich. 



13 6. A pair of large setal papillae on the tenth and twenty - 



first segments, and smaller ones on the eleventh and 

 twelfth segments ' . M i c r o c h aj t u s i v a r i Mich . 



14 a. Glitellum begins far back, at least behind the twenty- 



fourth segment . . . .15 



14 b. Clitellnm includes segments 14-16. . .16 



15 fl. Setae strictly paired. Clitellum begins on the twenty- 



seventh or twenty-eighth segment, and reaches as far 

 as the thirty-fourth or thirty-fifth. Distinct copulatory 

 walls on segments 31-33. 



Helodrilus caliginosus (Sav.) f. trapezoides (Dug.) 



15 b. Setae widely paired. Clitellum extends from twenty-sixth 



to thirty-first or thirty-second segment. Copulatory 



walls indistinct or absent. . Helodrilus constrictus (Rosa) 



16 a. Two pairs of prostate pores on seventeenth and nine- 



teenth segments, those of each side united by a longi- 

 tudinal seminal furrow. . . . .17 



16 b. One pair of prostate pores or a single median one . *22 

 17a. Setae ventrally widely paired; dorsally separated (del- 

 ed) ...... 18 



17 b. Sette strictly paired. . . • .21 



18 a. Head tanylobous; tlie dorsal appendix of the prostomium 



reaches as far as the furrow lietween the first and second 

 segments. Clitellum extends from the thirteenth to 

 the eighteenth segment ; it may not begin until the 

 middle of the thirteenth. . . C hi lo t a bra un si ilfic/i. 



18 b. Head epilolious, the dorsal appendix of the prostomium 



does not reach as far as the furrow between the first 



and second segments. . • .19 



19 a. Clitellum extends from the fourteenth to the sixteenth 



segment, ring-shaped, but ventrally somewhat lower. 



Chilota wahlbergi MicliA. typicus 



19 b. Clitellum occupies at least a portion of the seventeenth 



segment. . . . • • ■^O 



20 a. Clitellum extends from tlie middle of the twelfth segment 



to the middle of the seventeenth segment. 



Chilota triigSrdhi Mich, 

 a Length. 80-105 mm. ; diameter, lf-2^ mm. f . typicus 

 j8 Length at least 130 mm., diameter 3^-4 mm 



var. major n. var. 



' The constancy of these characters is questionable, and it is advis- 

 able to examine the internal anatomy for distinguishing these species. 



