262 THE ANNELIDA POLYCHAETA. 



The branchiae begin on somite IX and occur on succeeding somites to the 

 end of the body, excepting on the last two or three. They are short and incon- 

 spicuous, being exceeded in all cases by the cirri; erect and mostly free from the 

 dorsum. They are throughout unilaterally pectinate, the stem arising from base 

 of notocirrus and slenderly tapered. Filaments arising nearly at right angles 

 to the stem, close and often crowded, parallel, slender, two thirds or less the 

 length of the cirrus. They are simple but often branch a little above origin 

 into two filaments which are usually equal but may be unequal in length. The 

 first branchiae have four or five filaments, the second about eight, the fifteenth, 

 sixteen or seventeen, counting the terminal extension of the stem, of which two 

 are divided near their origins, making the total number of filaments eighteen 

 or nineteen, and the thirty second branchiae have again but eight or ten filaments. 

 (Plate 57, fig. 2). 



The acicula are black and opaque. In the anterior parapodia there are 

 two acicula with their tips, which are paler, projecting among the bases of the 

 dorsal setae and two or three much finer and closely appressed acicula extending 

 into the base of the notocirrus. Farther caudad the dorsal acicula become 

 reduced to a small and inconspicuous fascicle of fibers. The two ventral aci- 

 cula are stout and black throughout, with their tips projecting farther than in 

 the anterior parapodia; the tips are acutely pointed, and are either straight or 

 very weakly curved. The setae are comparatively long, all clearly exceeding 

 the neurocirrus, though much shorter than the notocirrus. Those of the dorsal 

 fascicle are much longer than the ventral ones. In the dorsal fascicle the princi- 

 pal setae are about twelve in number. They are distinctly margined or winged 

 along two sides; the distal end is narrowed to an acute point and is curved; 

 they are obliquely striate, though the striae are not always pronounced. (Plate 

 57, fig. 3). Among the limbate setae are the much shorter pectinate ones. 

 These have the usual slender stalks bearing the cuneately widening distal bodies 

 which are finely pectinate along the distal margin; the marginal process, or 

 mucron, borne at one edge is fine and short, or but moderate in length. The 

 less numerous setae of the ventral fascicle are compound. Their shafts are 

 moderately curved and are strongly clavately widened distad; the appendages 

 are short and distally bidentate, the upper tooth in the form of a hook, the infe- 

 rior one much larger and projecting at right angles to the axis of the process; 

 process widening proximad, with no distinct basal tooth; the usual delicate 

 guard, which, but shghtly or not at all, extends beyond the tip of the process; its 

 edge very finely denticulate. (Plate 57, fig. 5). In each parapodium of the 



