322 THE ANNELIDA POLYCHAETA. 



neurocirnis is reduced to a low rounded elevation or tubercle. (Plate 37, fig. 3). 

 On succeeding parapodia caudad the notocirri gradually become reduced both 

 in length and diameter, finally in the posterior region appearing as mere rudi- 

 ments or tentacles, and then quite disappearing. (Plate 37, fig. 4). The 

 neurocirrus is reduced to a scale-like body in the glandular area, as usual in 

 Onuphis. The postsetal process caudally becomes gradually reduced, appear- 

 ing soon as a merely sUght, rounded, elevation, and not at all evident after the 

 thirteenth parapodia or near them. The parapodia after the third become 

 attached near the middle of the somite and shift to a more dorsal position, as 

 usual. Through the middle region they continue as moderately prominent 

 processes, but in the posterior region they become more shortened. Through- 

 out the length the parapodia continue to project in a distinctly ectocephahc 



direction. 



The ordinary crochets, occurring on all but the more anterior somites, are 

 long, coarse, transparent setae, which are straight except toward the distal end, 

 where they are gently curved; they are of essentially uniform diameter until 

 jiarrowed in the usual way below the cervix, or they may appear a little thicker 

 just below this region; the medulla is finely, obhquely fibrillate in the distal 

 portion; they are bidentate, the teeth obhque and subparallel, rather slender 

 and acute, with the subapical one the longer; the membranous guards rise 

 conspicuously above the apical tooth and are narrowly, subacutely rounded at 

 the tip. (Plate 37, fig. 7). The delicate pectinate setae are numerous and 

 form a prominent fascicle, more dorsal in position; the stalks are comparatively 

 long, and the end-piece is cuneate in outline, but forms really a hollow half cone, 

 with a fringe of uniform and rather short teeth along the distal edge. (Plate 37, 

 fig. 5). Below the fascicle of pectinate setae is a series typically of four long, 

 stout, limbate setae; each of these is typically moderately bent near the begin- 

 ning of the distal third, which is acuminate and ends in a fine tip; the seta is 

 bilimbate, the wings widest at the bend, and from there they narrow each way 

 and so soon disappear. (Plate 36, fig. 5, 6). The acicula are pale; they are 

 stouter than the coarse limbate setae and most of the buried portion is of nearly 

 uniform thickness; a little below the surface each aciculum begins to narrow, 

 and above the surface is rapidly attenuated to a fine tip. (Plate 37, fig. 6). 

 On each of the first parapodia there are three stout setae or crochets of special 

 character; these are weakly and moderately ciu-ved, are unjoin ted, and are 

 apparently rounded, with but a slight indication of a tooth set off by an incision 

 below tip; each tip is protected by two membranous guards that rise above its 



