258 PROCEEDINGS OF THE ACADEMY OF [April, 



the direct continuation of the base of the notocirrus, which they dis- 

 place ventrally or toward the neuropodium. The first is always much 

 more slender than the notocirrus, but nearly as long. By somite X 

 the gill is three times as long as the notocirrus, and when, on middle 

 segments, its maximum size is reached is fully four times as long and 

 reaches well beyond the mid-dorsal line except on one specimen, on 

 which they are strongly contracted. All of the gills, which continue 

 nearly to the caudal end, are coarse round filaments apparently not 

 at all ligulate and contain two large longitudinal blood-vessels con- 

 nected by a large number of semiannular transverse vessels. 



Neuropoclial acicular three or four stout, tapered rods with mucro- 

 nate tips projecting freely beyond the surface antero- ventral to the 

 curved series of capillary setse from which they are not sharply dis- 

 tinguished. Notopodial acicula a fascicle of a few very slender and 

 delicate fibers passing through the notopodial base and far into the 

 notocirrus. 



Setae are of five forms, all but the yellow posterior crochets being 

 colorless. The first five neuropodia bear a nearly complete circle 

 enclosing the acicula, of semi- articulated, tridentate, guarded crochets 

 (PL XV, fig. 26) and simple capillarly setae differing little from the 

 acicula save only in their longer projecting points. The latter increase 

 in number and in size and in parapodia immediately following the 

 fifth (VI) replace the crochets. In the course of ten or twelve segments 

 they gradually disappear. All parapodia, beginning with the sixth, 

 bear a curved fascicle dorsal to the postacicular lobe of delicate, nearly 

 straight, capillary setae which, on anterior segments, are provided with 

 a narrow limbus not discernible posteriorly. Among the bases of 

 these are very delicate setae ending in gouge-shaped expansions bearing 

 eighteen or twenty regular mucronate teeth (fig. 27). Beginning at 

 about XVII two large and stout crochets appear antei o- ventral to the 

 acicular papilla; their shafts are slightly curved and distally thickened 

 and the little projecting ends bidentate and enclosed between a pair 

 of guards (fig. 28). 



Jaws described from a single dissection of a eotype (station 4,401). 

 Mandibles (PI. XVI, fig. 36) pale brown with pure white masticatory 

 plates, soft, the two halves only very slightly joined by the bases of 

 the masticatory plates, the long slender stems or carriers widely 

 separated and of nearly equal width throughout. Masticatory plates 

 white with a black trifid spot near the base of each, narrowly ovate 

 quadrilateral with obscurely bidentate end. Maxillae (fig. 37) rather 

 soft, pale brown with certain very dark lines and thickenings as shown 



