igog. 1 J. Stkphknson : Aqnalic ajiiinals fyoiii Tibet. 109 



Two eyes are present as pigmented patches situated laterally 

 at the level of the anterior lip of the mouth. 



The pharynx occupies segments iii — v, the oesophagus vi, and 

 a dilatation (stomach) of somewhat irregular shape appears in seg- 

 ments vii — viii. Posterior to this, the intestine is widely and re- 

 gularly dilated in each segment. The anus is slightly dorsal. 



The discrimination of the various species of the genus Nais 

 depends largely on the characters of the seta^. Though the present 

 specimen does not agree exactly with any form hitherto described 

 (coming closest perhaps to ;V. obtiisa, Gerv.), I prefer not to 

 erect a new species on the Ijasis of a single preserved specimen, 

 especially as the dorsal setal bundles are largely incomplete. I 

 myself examined previously some scores of living examples of a 

 Nais common at I^ahore before arriving at what I considered an 

 adequate description of the dorsal setal bundles. 



Fndericia stewarti, sp. nov. 



No. 32. Jligh Hill Gompa, Gyantse, Tibet ; 14,500 ft ; 28-iii-o7. 

 Six specimens, mostly with sexual organs (ova and yolk). 



Length 8 to 22 mm. Colour yellowish. Segments about 45 

 (43 — 46). Prostomium short, rounded; external annulation fairly 

 well marked. Clitellum on segment xii and most of xiii ; may 

 spread partly over xi. Epithelium of surface markedly thicker 

 over prostomium. Head pore apparently between prostomium and 

 segment i ; dorsal pores not distinguishable in my preparations. 



The setae {v. text-fig. i) are in four bundles per segment, two ven- 

 tral and two lateral; they are of the same character 

 J in all the bundles, being comparatively small with 



.•••"■ ■ .single blunt point, free extremity very slightly 

 li hooked, shaft straight or only curved in the 



slightest degree. They are arranged in fan-shaped 

 form transversely in each bundle ; those in 

 the centre of each bundle are the smallest, and 

 their size increases gradually towards the outer- 

 most components of the bundle, these latter be- 

 ing thus the longest. Each bundle is thus typi- 

 cally made up of a number of pairs of setae, the 

 members of a pair being of the same size, situa- 

 FiG. I— A seta ted one on each side, and separated by the inter- 

 of Friderioia stew- position between them of the smaller setae of the 

 aril ; d. = its distal bundle. In cases where the bundle consists of 

 an odd number of setae it can often be seen that 



1/ 



one pair is incomplete, owing to the dropping out of a seta on one 

 side. The arrangement is that peculiar to the genus. The num- 

 ber of setae per bundle varies ; posteriorly there are commonly 4 

 to 6 or 7 laterally, and 6 or 7 ventrally ; anteriorly there are often 

 more, most frequently perhaps 7 laterally, and 8 ventrally ; 9 and 



