EREANTIATE POLYCHAETA OF JAPAN. 173 



The reproductive elements are ripe in Kojima Gulf in the 

 month of Deccml)er. 



Nereis exoensis n. sp. 

 PI. XVIII, figs, 12—20. 



Body tapering posteriorly; brown or brownish gray; 95-100 

 segments. Prostomium as broad as long ; tentacles longer than J 

 its length, touching one another at their base ; palpi thick, their tip 

 not reaching to that of tentacles. Peristomium twice as long as 

 the succeeding segment ; inferior tentacular cirri not extending 

 beyond tentacles, the longest superior ones reaching to 4th segment. 



Parapodia increase their length posteriorly ; the rami 

 slightly separated from each other ; conical lip of dorsal ramus 

 a little longer than ventral ramus ; superior ligula conical, 

 extending beyond the latter a little in anterior parapodia, but 

 mucli in posterior parapodia. Dorsal border of dorsal ramus 

 elevated, scarcely convex in anterior, but strongly so in 

 posterior, parapodia ; inferior ligula simple and conical, as long 

 as ventral ramus. Bristles with either falcate or setose end-piece. 

 The falcate end-piece of bristles much longer in this species than 

 in the closely allied Nercii^ vexillosa'^' 



Dorsal ciri/iis filiform, extending far beyond parapodium. 

 Ventral cirrus on a basal knob at base of parapodium, not so 

 long as inferior ligula. 



Proboscis stout. Paragnathi : T. single or none ; II. in four 

 irregular rows ; IV. in curved groups ; III. a transverse group consist- 

 ing of Tj-f) rows : A', absent ; VI. a small group of — 8 ; VII., 

 \lli. a transverse l)an(l consistinL' of an anterior row of irregularly 



* Ehi.kks: — nio IJorsteinvürnior p. 57:5, 1808. 



