ONUPHIS SOCIA. 285 



and a maximum width of about 3.2 mm. It is composed of about one hundred 

 and forty-five somites; but a large paratype from Station 4666 is 178 mm. long, 

 and, though its width is the same as in the type, the number of somites is two 

 hundred and seven. 



The prostomium is short and subcylindrical, being slightly narrowed 

 anteriorly and in anterior view circular in outline. Above it presents a median 

 longitudinal furrow from the base of the median tentacle caudad; and in front 

 the area within the base of the tentacles is flattened. The tentacles are 

 arranged in a circle. The frontal tentacles are short, subcylindrical processes 

 subconically rounded distad and sometimes a little constricted toward base; 

 they are separated by rather less than half their diameter; the prostomium 

 beneath them is but slightly carried forward. The frontal tentacles, as in allied 

 species, consist each of a long ceratophore bearing a much more slender, finely 

 attenuated style. The ceratophores are nearly strictly cylindrical and are 

 strongly and closely annulate, the annuU being short and numerous, the con- 

 strictions separating them distinct, but often not deep. The tentacles of the 

 first pair reach to the anterior half of somite II, their tips attaining the bases 

 of the first parapodia, or in some cases reach toward the caudal end of the somite. 

 In these the style varies from rather less than twice as long as the ceratophore 

 to somewhat more than twice as long. The ceratophore in the type is composed 

 of five annuli of which the most distal is longest and the two immediately proxi- 

 mad of it the shortest. The posterior paired tentacles in a paratype reach to 

 somite VII, which is probably the usual proportionate length, but in some 

 appear shorter. In the type they do not extend beyond somite III. The 

 ceratophores are longer and much stouter than in the first pair ; each is composed 

 of six articles of which the most distal is longest and the three preceding it are 

 shortest and subequal to each other; in the larger paratype from Station 4666 

 the ceratophore is composed of nine articles, the very short additional rings 

 being found adjacent to the distal one. 



The median tentacle, as in others of this group of species, is much shorter 

 than the adjoining posterior laterals, reaching only to the third somite. Its 

 ceratophore is decidedly shorter than that of the posterior laterals, being about 

 equal in length to that of the anterior laterals, though decidedly stouter; it is 

 composed of five annuH, of which the most proximal and most distal are longest. 

 The palps are large, conspicuous bodies, stout, and subcontiguous at the median 

 line and conically narrowed distad, the two diverging from each other, the axis 

 of each extending ectoventrad. 



