348 THE ANNELIDA POLYCHAETA. 



and is attached along one entire edge, only the acute distal tip being free, this 

 projecting distoventrad at the edge of the ligula. (Plate 63, fig. 5). 



In a typical parapodium of the posterior region, as in the thirty seventh, 

 there are two pale transparent acicula, of which the neuropodial is distinctly 

 the stouter. The setae are all simple. They taper distad into fine tips, which 

 are normally curved. The setae are wholly smooth, lacking entirely both limbi 

 and teeth. They increase in length from the lowermost dorsad in the neuro- 

 podium and in the opposite direction in the notopodium, so that in the series 

 taken together those at the middle are longest, with the others decreasing 

 towards the ends of the series. In the thirty seventh and adjoining parapodia, 

 for example, the neuropodials number mostly from eight to ten, the notopodials 

 six or seven. In the parapodia of the anterior region the notopodial setae are 

 simple like those of the posterior region, but shorter and apparently more flexible, 

 being commonly much curved, often in a conspicuously sigmoid manner, and 

 differing more particularly in being narrowly limbate along one side, the limbus 

 finely cross-marked or serrate. (Plate 63, fig. 6). The neuropodial setae of 

 the anterior division are composite. The shaft ends distally in a socket of inter- 

 mediate type, one edge rising considerably higher than the opposite one. The 

 end-piece is long and varies much in size. It has a finely pointed, curved tip 

 and is narrowly limbate along one side, the limbus being finely cross-striate, 

 or vaguely serrate, as in those of the notopodial setae. (Plate 64, fig. 1). There 

 are thus three distinctly marked types of setae, two represented in the notopodia 

 and neuropodia respectively of the anterior parapodia, and one represented in 

 the parapodia of the posterior division. (Plate 63, fig. 7). 



The proboscis is wholly retracted, and, as it is thought best not to dissect 

 the single specimen at this time the armature is not described, — and it is likely 

 to have been lost under any conditions. 



Locality. Gilbert Islands: off Arhno reef. Taken at surface by night 

 light. One male. 24 January, 1900. 



This form has colorless, semitransparent tissues similar to those of most 

 other pelagic annelids. The uniformity in the characters of the simple setae 

 of the posterior region, with the contrasting character between notopodials and 

 neuropodials of the anterior region, are, perhaps, the most distinctive of the outer 

 structural features. 



Hemipodus Quatrefages. 



Hist. nat. anneh's, 1865, 2, p. 194; Arwidsson, Bergens mus. aarsbog, 1908, no. 11, p. 27. 

 llemijmlia Kinbcrg, Ofver K. vet. akad. Forh., 1865, no. 4, p. 245. 



