274 DISCOVERY REPORTS 



second specimen on the right side the posterior prostate is very reduced and confined to 

 one segment, and the short gland is doubled back on the duct. The penial setal sac 

 muscles originate from the body-wall of segment 19 near the posterior septum and the 

 bundles of setae lie irregularly, the b bundle twisted in front of the a and pointing up 

 instead of downwards. On the left side a similar condition prevails except that the 

 prostate is apparently entirely absent. The penial setae are apparently normal. 



Penial setal sac muscles originate, in part, from the body wall of the segment in which 

 they lie, and in part fibres pass back with the prostatic gland and appear to enter the last 

 septum through which the gland passes. Penial setae of two sorts, those of the a bundle 

 more slender than those of the b. In the a setae the stem is straight except for the distal 

 fourth which is strongly curved; the full-grown seta is about 1-5 mm. long and tapers 

 very gradually to a filiform point. The distal end is ornamented on the inner side of the 

 curvature with large, projecting, irregularly placed, serrate scales ; these stop abruptly, 

 and the tapering region beyond is ornamented with very fine, irregularly placed, simple 

 or serrate teeth (Fig. i b) ; in the middle of the stem the diameter is from 12 to 14 /x. In 

 the b setae the stem is straight except at the distal end, which is slightly curved and 

 tapers gradually to a filiform point ; in this region the seta is quite smooth, but lower 

 down it is ornamented at the distal end with alternating, serrate scales (Fig. i rt) ; a full- 

 grown seta is about 1-5 mm. long and in the middle region of the stem about 21-5/^ in 

 diameter. 



Spermathecae, two pairs in segments 8 and 9, similar to those of M. falclandicus and 

 M. georgianus. 



Observations. Beddard's original description of M. oquanimdulcmm is very in- 

 adequate, but it is probable that the specimens discussed above are correctly referred to 

 this species. As stated by Beddard for the types of M. aqiianimdidchim, these specimens 

 are verj^ similar to M. falclandicus, but more slender, and the body wall is thinner. Un- 

 like the types these specimens are not smaller, but of about the same length as specimens 

 of M. falclandicus ; this character is of doubtful significance. Beddard evidently only 

 observed the penial setae of the b bundle which he describes. In stating that the large 

 tubercles of M. falclandicus are entirely absent he was in error, since the projecting 

 serrate teeth of the a setae are not unlike those of the latter species. 



This species is also in close agreement with M. anderssoni Mich. The prostatic duct 

 is not in any sense of the word short as described for M. anderssoni, and the ornamenta- 

 tion of the penial setae seems to be somewhat different. It is quite possible that these 

 differences are not significant and that the two species should be synonymized. 



M. aquarmndulcium cannot be distinguished from M. falclandicus with any certainty 

 on external characters. It is undoubtedly more slender and owing to the greater thinness 

 of the body-wall the more extensive prostates can as a rule be seen from the outside. On 

 internal characters it is chiefly distinguished by the greater extent of the prostates and 

 by the form of the penial setae. 



