36 



Transactions. 



Another peculiar feature is that the duct of each of the two sacs opens 

 into a large muscular "" atrium," which in its turn opens to the exterior. 



The penial sacs are large, and the penial chaetae long. These are 

 bluntly pointed, and the edges are curved upwards so as to form a short 

 shallow furrow extending a short distance from the apex (fig. 2). These 

 edges are ornamented with a few short bluntly pointed processes, but the 

 rest of the chaeta is smooth. I examined not only a fully developed chaeta, 

 but also one of the reserves, which exhibit precisely the same features, so 

 that the processes are not produced by wear of the edges. 



Fig. 1. — Maoridrilus megacystis. Spermatheca. a, muscular " atrium " 

 common to the ducts of the ampulla and the diverticulum (rf) ; s, septum. 



Fig. 2. — M. megacystis. Tip of a penial chaeta, imder a high power. 



Fig. 3. — Maoridrilus iliomsoni. View of the ventral surface of segments 15-21 

 ( X 4^), showing the characteristic " trough " and the position of the 

 ventral nephridiopores. 



Fig. 4. — M. thomsoni. Spermatheca. 



Fig. 5. — M. thomsoni. Penial chaeta. 



Locality. — Stephen Island. 



RefMirks. — The only species at present known in which the dorsal vessel 

 is single throughout the body is M. michaelseni Ude (2), which was collected 

 at Westport ; but in that species the diverticulum of the spermatheca is 

 quite small, its duct is narrow, and there is no " atrium " ; further, the 

 penial chaetae are quite different. The size of the diverticulum suggests 

 the specific name, 



M. thomsoni n. sp. 



Of this species also there is but a single individual, which seems to be 

 of about the same size as the previous species, but is in even a worse state 

 of preservation than it. It is damaged just behind the clitellum, and is 

 very soft. Its posterior end is missing, and there is as yet no sign of 

 tapering. We do not know, therefore, what is its length. The fragment 

 contains 198 segments and measures 65 mm. in length. The first 24 seg- 

 ments contribute 10 mm. to this.* Its diameter behind the clitellum is 



* In the previous species this anterior region accounts for 25 mm., but I did not 

 make corresponding measurements of the other features, for I had opened it before 

 studying the present worm. 



