1911.] NATURAL SCIENCES OF PHILADELPHIA. 279 



of XIX, none on XX and then from both sides of XXI caudad. On 

 both specimens they continue to increase in length gradually and 

 probably reach their maximum size at XXIII where they about reach 

 the dorsimeson and are five to six times the length of the dorsal cirrus, 

 the length of which, indeed, scarcely exceeds their diameter (fig. 88). 

 They have the usual structure, being coarse filaments containing a 

 large axial blood-vessel, and within the limits of the piece exhibit no 

 indication of becoming flattened. 



Neuropodial acicula pale yellow, generally three, but posteriorly 

 only two, stout, tapered, slightly curved, the pointed apices projecting 

 only slightly beyond the integument. Notopodial acicula a small 

 fascicle of fibers. 



Setae of four kinds. The first three parapodia bear a few stout, 

 compound crochets in a vertical series. They are especially large 

 on the first and project freely forward. On the second and third 

 parapodia (fig. 89) they become smaller and paler in color. None 

 seem to be truly compound, but the oblique joint is imperfect and near 

 the end. The shaft or portion of the setae proximad of this interrup- 

 tion is slightly thickened in its distal portion and minutely roughened, 

 partly with minute imbricated, antrorse scales and partly with minute 

 hairs. The distal piece or appendage is somewhat recurved, tapered 

 to the peculiarly formed bidentate tip, which is enclosed in a pair of 

 broad obliquely truncate guards. It is possible that larger specimens 

 (should such occur) would lose some of these characters through wear. 

 Beginning on the fourth foot (V), the compound crochets (one or two 

 of which may remain, though there are none on these specimens) are 

 replaced by simple setae which are characterized by a finely roughened 

 enlargement beyond which they taper to an acute curved tip. Farther 

 back these setae are partly reduced in size, but chiefly transformed into 

 small supra-acicular and subacicular fascicles of simple setae with 

 broadly bilimbate, lanceolate blades (fig. 91). Associated with these 

 setae in the dorsal fascicle, beginning on the second foot is a dense 

 tuft of very delicate pectinate setae, the abruptly widened end of which 

 (fig. 92) is bent into semicircular form and bears about thirty regular 

 and equal teeth and mucrons. On posterior segments they become 

 much wider and flatter. Beginning at about somite XX, two stout, 

 yellow, slightly clavate, bluntly rounded bidentate and guarded 

 crochets appear in the subacicular fascicle of each crochet (fig. 90). 



Jaws thin and fragile, but hard and well-chitinized. Mandibles (figs. 

 93 and 94) pale brown, with some dark streaks, the stems regularly 

 tapered, slightly enlarged at the distal end where the two are feebly 



