SPECIES OP THE GENUS AULODRILUS. 963 



(4) AULODRTLUS STEPHENSON I, Sp. n. 



All the worms I obtained conform to the above description 

 with the exception of one. This was first examined in the living 

 condition and then studied from longitudinal sections. The 

 description, though far from complete, gives the main features of 

 the anatomy. 



(a) External Characters. 



The length is about 17"5 mm. The prostomium is bluntly 

 conical. The number of segments is 56. The spermathecal 

 openings lie on the ventral surface in the 9th segment much in 

 front of the ventral setse. The spermiducal chamber lies on the 

 ventral surface of the 10th segment : as it is very shallow, the 

 opening of the atrial duct is clearly seen in each of its antero- 

 lateral corners. During the examination of the living worm this 

 chamber was not made out and the openings of the atrial ducts 

 were supposed to be paired male openings ; but the closer 

 examination of the entire mount and subsequently the sections 

 revealed the presence of the shallow chamber. 



Setoi. — Dorsal and ventral setae are present in all the segments 

 from the 2nd segment backwards. The dorsal setee are about 

 3-9 per bundle, each bundle being composed of 2-3 hair setse, 

 and 1-6 sigmoid needles. The uncinate seta (text-fig. 8) is about 



Text-figure 8. 



Uncinate seta of A. stejohensoni as seen in balsam preparation of the 

 entire specimen. X 540. 



half the size of the hair seta and ends in a fine point at the distal 

 extremity. The small narrow outer process, or the distal prong 

 which is present in the setse of A. kashi, is not seen. It may be 

 that its absence is due to breakage while making preparations. 

 The nodulus is situated at about one-third of the distance from 

 the distal end, and the distal portion of the shaft beyond it 

 projects outside the body-wall. 



The ventral setse are similar to the dorsal needles and are 7-10 

 in a bundle. The penial setae are the modified setse of the 10th 

 segment and are 1-2 in a bundle ; they lie in the spermiducal 

 chamber slightly outside the opening of the atrial duct. In shape 

 and length they appear like those of A. kashi; the breadth near 

 the base is about 5-7 /*. 



