1911.] NATURAL SCIENCES OF PHILADELPHIA. 265 



exclusively (except perhaps the dorsalmost) semicompound, bidentate 

 and guarded crochets with the articulation very imperfect and the 

 guards much prolonged and very acute. None of these setae is much 

 enlarged and the dorsalmost is very slender and acute and may lack 

 the hooked and bifid tip. The second and third parapodia have a 

 few similar setse in the anterior part of the fascicles, together with a 

 few simple acute setse in the dorsal part. On the fourth foot . all 

 setse are of the latter tjq^e. Toward the distal end they become 

 somewhat enlarged and minutely pilose, but not truly limbate and then 

 taper to an acute tip. On the fourth parapodium there are only seven 

 of these setse, four being anterior and three dorsal, the latter more 

 slender. Simple setse of this type appear on all subsequent parapodia, 

 but after a few segments are limited to a small dorsal fascicle of two 

 to four and gradually become more slender and elongated toward the 

 caudal end. Pectinate setse (fig. 55) first detected on IX and present 

 on all following segments as a small dorsal tuft of three to six. They 

 are extremely delicate and have slightly curved asymmetrically ex- 

 panded ends with the margin distinctly denticulated. Two large 

 ventral crochets (fig. 56) appear on X, but become larger and more 

 exposed farther back. They are peculiar in the length of the beak 

 and small size of the accessory tooth and the somewhat un\isual width 

 of the guards. Toward the caudal end they become much smaller 

 and one has the teeth reduced and the other more or less straightened 

 out and the guards are frequently absent (fig. 57). 



Jaws (PI. X\TII, figs. 98-99) pale brown or yellow, translucent, 

 soft, and flexible. Mandibles very delicate, the carriers slender, 

 widening very little distally, feebly united, the masticatory plate 

 narrowly elliptical, prolonged forward, a small tooth on the medial 

 side. Maxillse (fig. 99) with acute, strongly hooked forceps jaws, the 

 carriers about two-thirds as wide as long, each half ])rolonged into a 

 slender posterior process. Alaxilhe II Iwoad plates, the left outer with 

 eight or nine teeth, the inner with seven or eight, the right with nine 

 or ten larger teeth; III, left five or six teeth, right seven or eight teeth ; 

 IV rudimentary, edentulous. 



Nearly all of those examined are practically colorless, the anterior 

 end more opake and iridescent. Some examjiles from station 4.454 

 have the cephalic appendages dark or black and conspicuous quadrate 

 blotches of black scattered over all parts of the Ijody both doi-sally and 

 ventrally and on parts enclosed by the tubes as well as parts exposed. 



Tubes generally about 45 nun. long and 2 nun. to 2.3 nun. in diameter, 

 tapering off at one end to a tliin membraneous portion. The thicker 



