1911.] NATURAL SCIENCES OF PHILADELPHIA. 303 



into a dorsal and a ventral lobe. On anterior segments (fig. 157) 

 these present no striking peculiarities; both are foliaceous at the 

 base where the ventral lobe is much the larger, while the distal portion, 

 which is separated by a slight constriction, is longer and acute in the 

 dorsal lobe and usually obtuse in the ventral lobe. Neurocirrus 

 prominent, attached to middle of ventral face of neuropodium, some- 

 what grooved and embracing the neuropodium at the base and tapered 

 to an acute tip which usually diverges more or less from the foot. 

 Notocirrus a small globoid or subcylindrical papilla situated on the 

 side of the body well above the parapodium. Passmg caudad, the 

 foliaceous base of the dorsal presetal lobe is gradually reduced and the 

 distal part enlarged to form a gill which becomes fully established at 

 about XXXV (fig. 158). Throughout the middle region and nearly 

 if not quite to the caudal end this lobe forms a prominent, subligulate, 

 erect gill rising from the dorsum of the end of the foot and fully equal- 

 ling or exceeding the latter in length (fig. 159). The ventral presetal 

 lobe does not become branchiform, but elongates and finally takes a 

 slender finger-like form (fig. 159). Simultaneously with the develop- 

 ment of the dorsal gill a ventral gill develojjs from the modification 

 of the neurocirrus. This is similar in form to the dorsal gill, but when 

 fully developed (figs. 158, 159) becomes even larger, reaching beyond 

 the end of the postsetal lip. Near the caudal end it undergoes con- 

 siderable reduction in size. Both dorsal and ventral gills are thin- 

 walled and sacular with large cavities communicating with the cct'iom 

 and a layer of longitudinal and slightly oblique muscle fibers by which 

 they may be retracted. 



Acicula two, corresponding to the two principal fascicles of setap, 

 • both simple, nearly straight, tapered, pale rods, the ventral much 

 the stouter. Setie colorless, in three fascicles, a dorsal obli<:|ue row 

 of very slender simi:)le seta\ a middle horizontal and a ventral vertical 

 series of compound seta^. The latter have slender shafts terminating 

 in deep asymmetrical sockets and slender, tapered, finely punctated 

 blades, with minute marginal denticulations. On the first two j^ara- 

 podia simple setne are absent, but the dorsalmost com])Ound seta> have 

 very long slender blades. In general the blades of the compound 

 setae decrease in length from the dorsalmost ventrad and fiom the 

 anterior end caudad. 



I^roboscis described from a cotype (station 4,517), this being the 

 only one in which it is everted to the jaw pads. The nearly complete 

 worm is 35 mm. long, the proboscis 12 mm. long, 1.5 mm. in diameter 

 at the base and 3.2 mm. at the distal end. Clavate, the distal end 



