Oliqochaeta. 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



275 



Notiodrilus macquariensis, Beddard. 



1896. Acanthodrilus macquariensis, Beddard, Proc. Zool. Soc, p. 208. 1900. 

 Notiodrilus macquariensis, Michaelsen, " Oligochaeta." 1901. Benham, 

 Trans. N.Z. Inst., xxxiii, p. 132. 1907. Microscolex macquariensis, 

 Michaelsen, Die Fauna S.W. Austral., p. 143. 



I gave a detailed account of this species in 1900. Although the Macquaries 

 were not included in our expedition, as it is not under the Government of New Zea- 

 land, yet I include it in this report as a link with the other subantarctic islands. 



XV 



Plagiochaeta, Benham, 1892, 

 Plagiochaeta plunketi, sp. no v. (Plate XI, figs. 18-20.) 



A single individual. 



Colour dark violet, even after eighteen months in formol. Each of the pre- 

 clitellar segments has a pale chaetal ring round it. The clitellum is uniformly violet- 

 grey posteriorly ; a narrow line of bluish-grey runs along the median dorsal line. 

 This pigment is situated in the connective tissue of the circular and longitudinal 

 muscle-layers, not in the epidermis, except in the clitellum, 

 where it appears in amongst the gland-cells. 



Dimensions. — The worm is 70 mm. by 1*75 mm., and 

 consists of 112 segments. 



The jyrostomium is epilobic, |, without transverse groove. 



The clitellum, though not fully developed, as the chaetae 

 are still visible, covers segments 14-16 (17) ; it extends over 

 the ventral surface in the anterior portion, but leaves the 

 middle of the 15th and following segments free from gland- 

 ular tissue. 



The chaetae are 16 in each segment, 8 on each side, 

 throughout the worm. The spaces nb=cd=fg = ^hc; 

 be = de = ef = gh ; aa = 2 be ; hh = 2 ah — that is, the 

 dorsal gap is rather greater than the ventral. 



Dorsal pares commence at 12/13 segments. 



Nephridiopores in line with d or e. 



Genital Pores. — The single specimen was studied by 

 means of longitudinal sections, for it was so bent at the 

 critical point that it was impossible to make out accurately 

 the arrangement of the genital pores. The " porophores," 

 or papillae carrying the prostate pores, on segments 17 and 19 are in a deep 

 depression, owing to the contraction of strong dorso-ventral muscles of these 

 segments. 



The two most ventral chaetae are present on the median side of the pores. 

 There is no apparent ornamentation ; at any rate, none is visible in Canada-balsam 

 mounts. The lowest, a, is normal, but b is enlarged, and by no means so much 

 modified as usual. Each penial chaeta is stouter and longer than an ordinary loco- 

 motor chaeta, and is hooked terminally (Plate XI, fig. 19). 



jsxn 



JtESZ" 



Plaoiochakta pldnketi. 



Ventral view of the genital 

 segments, (x 10.) 



