igoS.] W. MiCHAEivSEN : Oligochœta of the Indian Empire and Ceylon. 



215 



OCTOCH^TUS THURSTONI. MlCHI^SN. 



(Plate xiv, fig. 36.) 



O. th., MICHAEI^SBN, in Mt. Mus. Hamburg, xxiv, p. 173, f. 17. 



Examined, three mature specimens. 



External Characters. — Dimensions: Length 130 — 160 mm., maximum 

 thickness 5|- — 6 mm., number of segments 198 to about 204. 



Colour greyish. 



Head tanylobous (?); lateral borders of the hinder appendix diverging back- 

 wards. Prostomium small. 



Setae moderately large, all at the ventral part of the body, the dorsal distance 

 being somewhat larger than half the circumference of the body {dd = ca. ju). 

 Setae paired, but not strictly, those of the lateral pairs almost as distant one from the 

 other as the median lateral distance {cd = csi. jbc), those of the ventral pairs a little 

 closer together {ab = ca. f&c). The median ventral distance is somewhat larger than 

 the median lateral {aa =ca. i^bc). 



Dorsal pores present, but distinct only from the intersegmental furrow 18-19 

 (missing anterior to it ?). 



Clitellum complete, but ventrally depressed from segment 13 — 17 ( = 5). 



Prostate pores on the 17th and 19th segments between the lines of setae a and b. 



Seminal furrows nearly straight. 



Male area a little depressed in all, but with a broad cushion-like elevation 

 between the seminal furrows. 



Female pores probably in the anterior median ventral part of the 14th seg- 

 ment, where a white glandular area is to be seen. 



Spermathecal pores two pairs on segments 8 and 9 between the lines of 

 setae a and b, just before and not far from the ventral pairs of setae of these segments. 



Copulatory organs : Two, three or four big and broad trans- 

 verse glandular cushions median ventral on some of the segments 

 behind the clitellum, the last at the 24th segment, beginning at the 

 2ist, 22nd or 23rd segment. The cushions reach as far as the 

 lines of setae b on either side, or not quite so far. 



Internal Anatomy, — Septum 5-6 rather strong, the follow- 

 ing, 6-7 and 7-8 (and 8-9?) missing, those of the anterior male organs, 

 8-9 (?) — 12-13, very strong. 



Alimentary tract : A big gizzard behind septum 5-6. A 

 pair of great calciferous glands opening into the oesophagus in 

 the 15th (?) segment, but occupying a space of more than one 

 segment (pushing back the septa ?). They are very thick, tightly 

 rolled up to an irregularly spiral form and are closely pressed 

 against the oesophagus and dorsal-medially against each other. 

 Externally they show deep furrows and incisions surrounding big 

 cushion-like protuberances. The intestine contains a typhlosole, 



Fig. 23. 



Octochcetns ihiirs- 

 toni. 



