HARMOPSIDES NATANS. 49 



Body short. It is widest near the sixth somite from where it tapers con- 

 tinuously to the caudal end. The greatest width inclusive of the parapodia 

 is attained a little farther caudad, since the anterior parapodia are shorter than 

 the succeeding ones, those toward the caudal end also decreasing in length. 

 Dorsum convex, the venter less so and with a distinct neural ridge set off on 

 each side by a sharply impressed narrow furrow or sulcus. Length, 17 mm.; 

 greatest width, exclusive of parapodia, 2 mm.; width to tips of parapodia, 5.2 

 mm.; and to tips of setae nearly, 9.5 mm. Number of somites forty-four; 

 number of pairs of elytra, eighteen. 



The prostomium is wider than long. On each side it protrudes strongly 

 and angularly, the apex of the angle being at the middle of the length. It is 

 separated into two equal halves by a deep median longitudinal furrow. Each 

 half or lobe is prolonged directly forward into a terete and shghtly clavate 

 ceratophore which is somewhat constricted at the proximal end. Each eye of 

 the anterior pair is located on the protruding lateral angle of the corresponding 

 lobe. The eyes of the posterior pair are smaller in size, much closer together, 

 and dorsal in position. Each is separated by about twice its diameter from the 

 corresponding anterior one. The ceratophore of the median tentacle is inserted 

 anteriorly between the two halves of the prostomium. It is cylindrical, some- 

 what narrowed distad, and equal in length to the lateral ones. Proximally the 

 style is of the same thickness as the ceratophore but tapers continuously and 

 uniformly for about two thirds of its length and then more rapidly into a slender, 

 filiform, and acutely pointed tip. Its total length, inclusive of ceratophore, 

 is about four times the length of the prostomium proper. The styles of the 

 lateral tentacles are of the same form as that of the median but are more slender 

 and shorter. The palpi are comparatively slender. Each narrows from its 

 base continuously to a slender acute tip, and in length is equal to the median 

 tentacle or nearly so. (Plate 6, fig. 1). 



The peristomium shows distinctly above as a transverse band which is 

 small, with its anterior margin convex. The parapodia extend obliquely for- 

 wards, the distal ends of their cirrophores attaining the level of the anterior 

 margin of the prostomium. Each bears a stout spine or aciculum and three 

 small, curved, somewhat sickle-shaped, setae. Each cirrus tapers gradually 

 to a slender tip, the upper one extending distad the same distance as the palpi 

 while the inferior one is shorter. 



The parapodia are relatively long and, except in the anterior region, equal 

 or surpass the width of the somite to which attached. Proximad of the elytro- 



