370 OLIGOCHAETA 



Megascolex sylrestn's of HUTTON (1) may be congeneric or even identical with BENHAM'S 

 Plagiochaeta. I have entered into this question below. 



Perichaeta corticis is said to have 40 setae per segment, of unequal dimensions, to be 60 mm. long, 

 and to be composed of 114 segments. As VAILLANT (6, p. 88) justly remarks, these characters are 

 not enough to allow of our forming an idea of the relations of this species. 



Megascolex antarcticus of BAIRD (3) has also been examined by myself (61) as regards external 

 characters. The occurrence of a median genital papilla upon each of segments xvii and xix seems 

 to distinguish the species ; but there are no data as to the genus. I therefore leave it incertae sedis. 



Genus MEGASCOLEX, TEMPLETON. 



Syn. Perichaeta, AUCT. (in part.). 

 Anisochaeta, BEDDARD. 



DEFINITION. Perichaetidae, with circles of setae interrupted in the middle dorsal 

 a nd ventral lines, sometimes much fewer on anterior segments ; clitellum 

 generally occupying more than three segments. Gizzard in segment V or VI. 

 No intestinal caeca. Spermiducal glands lobate ; penial setae occasionally present. 

 Oviducal pores double. 



I have already gone into the history of this genus, which has been a somewhat 

 confused one. It remains now to review the species which are here referred to it. 

 There is not a great deal of variation in the genus. The most aberrant type is, 

 perhaps, M. ceylonicus, whose position in the system is doubtless a little dubious. 

 It is very characteristic of this genus that, in addition to the diffuse nephridia, there 

 should be a series of larger paired nephridia ; this occurs, for example, in M . armatus ; 

 nothing of the kind has ever been met with in the true Perichaeta. I refer 

 (provisionally) one species to this genus, which has paired nephridia only ; this worm, 

 M. deiidyi, may prove to be a Perionyx. It is possible also that the activity which 

 is found in all the species belonging to the genus Perichaeta (s. s.) is limited to 

 that genus ; the only species of Megascolex which I have had the opportunity of 

 seeing in the living condition is M. armatiis; in this species there was not that 

 sprightliness which I have seen in Perichaetae. The setae too in Megascolex are 

 not set upon ridges as in Perichaeta ; in consequence, when the worms are handled 

 the setae are not so evident to the feel. 



This genus is characteristically Australian in distribution ; it extends, however, into 

 the Oriental region, having been found in India, Ceylon, and many of the islands of the 

 Indian archipelago ; its comparatively limited distribution contrasts with that of its 

 ally Perichaeta, whose range is practically world-wide. 



