282 THE ANNELIDA POLYCHAETA. 



ninth has been reduced to a mere low, obtuse, angular projection and is not 

 evident on the following ones. The presetal margin is not in any case especially 

 elevated. (Plate 48, fig. 6, 7). 



The branchiae first appear on the sixteenth parapodia, i.e., on those of the 

 seventeenth somite. Each of the first branchiae consists of a single rather 

 stout filament a little exceeding the notocirrus in length. (Plate 48, fig. 8). The 

 second branchiae are bifurcate, with the filaments either equal in length or one 

 exceeding the other, or trifilamentous. The third and succeeding branchiae to 

 about the seventeenth are mostly trifilamentous, a long filament arising on the 

 anterior side close to the cirrus and making an angle of about forty-five degrees 

 or more with the other branch, which bifurcates farther distad, the branches 

 being either subequal or, more commonly, the caudal one smaller, often much 

 so; rarely a branchia occurs with four branches. (Plate 48, fig. 9, 10; Plate 49, 

 fig. 2). Caudad of this region the branchiae become mostly bifilamentous, one 

 branch being greatly elongated and the other more and more reduced. (Plate 

 49, fig. 3, 4). In the posterior region the branchiae consist of a single slender fila- 

 ment which undergoes gradual reduction until represented by a mere nodule 

 and finally quite disappears at about the twenty fifth somite from the caudal 

 end. (Plate 48, fig. 11). In the region of the twentieth and immediately follow- 

 ing somites the branchiae reach the middorsal line; at the thirtieth, and imme- 

 diately following, the long filament passes beyond the middle line. 



The dorsal setae of the anterior parapodia are slender and capillary, distally 

 acutely acuminate, and not at all limbate. The setae of the dorsal group of the 

 other parapodia are long, slender, and gradually reduced distad to a very fine 

 tip; they are normally curved distally and each is hmbate in the usual way, a 

 narrow wing on the side of the convexity in the curved distal part beginning 

 near or below the middle of the exposed portion of the seta and continuing to 

 the base of the bristle-like tip. (Plate 50, fig. 4). The pectinate setae occurring 

 among the bases of these limbate setae are short and delicate structures which 

 are large comparatively; distally each is clavately enlarged, the cuneate apical 

 piece being long, narrow, and asymmetrically prolonged distally on one side, 

 as usual. (Plate 50, fig. 5). The ordinary crochets first appear on or near the 

 tenth somite and occur on succeeding ones to the last of the series, there being 

 normally two in each parapodium ; they project more prominently in the poste- 

 rior region. In the posterior region they are stout, naiTowed distad, and biden- 

 tate at the tip; the apical tooth is very small and erect, the other much larger 

 one projects nearly at right angles to it and has its very tip bent distad, its 



