DESCRIPTIONS OF GENERA AND SPECIES 591 



Definition. Length, 45 mm.; breadth, i mm.; segments, 96. Fenial setae with transverse 

 rows of denticles at extremity. Eab.—Malahalla, Ti. Africa. 



This species is the smallest known Eudrilid. The setae are very deUcate, and 

 the distance between the four pairs is equal. There appears to be but little pigment 

 in the skin since the colour is described as being yellowish in front and grey behind. 



Genus Megachaeta, Michaelsen. 



DEPIBTITIOBT. Setae gradually diminishing in size dorsaUy, those nearest ventral 

 median line being largest. Male genital pore upon XVII. A single median 

 spermathecal sac opens on to segment XIII. Penial setae present. 



This genus is at present only imperfectly known, none of the examples of either 

 of the two species having been fully mature. These two species— ifec^acAaeto tenuis 

 and M. alba — are both East African. 



The most marked external peculiarity concerns the setae. The ventral setae are 



much stouter than the dorsal, and there is a regular diminution in size in passing 



from the ventralmost seta to the dorsalmost. Moreover in the anterior segments 



the setae are not so large as in the following segments. The characters of the setae 



are curiously paralleled in the genus Oordiodrilus (which see), which is not in other 



respects a near ally of the present worm. Michaelsen remai-ks that the nephridio- 



pores are not visible. It may be that this genus, like Libyodrilus, has an integumental 



plexus ; but we have no knowledge upon the point. The alimentary canal has 



a gizzard in segment v or vi; it appears to have neither calciferous glands nor 



ventral diverticula ; the genital organs are also imperfectly known. In Megachaeta 



alba only a single pair of sperm-duct funnels were found lying in segment xi. The 



spermiducal glands are , tubular and each has a sac of penial setae ; or rather a single 



seta belongs to each. The aperture upon the thirteenth segment leads into a sac, 



which extends back as far as the seventeenth segment. This sac gives off lateral 



outgrowths which communicate with compact glands attached to the septa. The 



nature of these is at present very doubtful, and they are ncrt very fully described 



by Michaelsen. The following is his description : — 



'Durch die Oeifnung im 13. Segment gelangt man in ein grosses muskulSses, sich auoh etwas 

 naoh vorne ausdehnendes Atrium. Nach hinten setzt sich dieses Atrium in sine lange unregelmassig 

 angeschwoUene und gekrummte Samentasclie fort, die sich bis in das 17. Segment erstreckt. Auch 

 die Samentasche ist muskulos, besonders ihr distaler Teil. Seitlich und unterhalb des Atriums und des 

 distalen Samentasobenendes baben siob starke Wucherungen gebildet, die bei einem ziemlicb unreifen 

 Exemplar flugelformig in die Leibesbohle hineinragten. Bei einem weiter ausgebildeten Exemplar zogen 



