1911.] NATURAL SCIENCES OF PHILADELPHIA. 



neurocirrus begins to undergo rapid reduction, and by the eleventh 

 its conical form and cirrus character are lost and it has assumed the 

 form of a low. smooth, rounded, opake and whitish swelling, which 

 increases in size to :. y\~. XXV and then diminish sg Though 



it remains - -mall whitish spot even at the end of the piece. The 

 postsetal lobe retains its character longer. unde:_ _ gradual 



i eduction after X and shifting more ventrad. Even ar. XX it is 

 as long as the body of the parapodium and of a short conical or sub- 

 triangular form. At L (fig. 60) it is a minute blunt papilla, ventro- 

 caudad of the sel and farther back disappears altogether. 



Xotocirri become more slender, but retain their length, continuing 

 reach the middle lir - r back at leasl 3 Hh ighty-ninth segmt 

 In the middle region the bodies of the parapo-:. reduced and 



hat compressed and bluntly rounded, and are situated near 

 the level of the dorsum. 



n the three specimens known the gills begin - single filame: its 

 on somites YIII or IX and never r ssess more than four filame: its 

 and that number only rarely. Two filame: its pear at from XXII 

 to XXVI. three at from XXXIII to XL and continue toLVI or LXLX 

 where the number is reduced to two again and a atm es :o the end 

 of the several pieces Not infrequent:; segment 1 



_:11 on one or both sides and frequently the number of filamenT- is 

 below the normal of the region. The gills, though of few filame^:s 

 are typically pinnate (fig ; aid the filaments rather thick and sh 



the longest very constantly reaching just : he median line. They 

 arise on the dorsal side of the notocirri on a common notopodial base. 



Acicula of anterior neuropodi s .illy three, yellow r si pered. 



gently cirrved and terminated by long freely p: ing mucron 



tips. On posterior neirropodia there are often only r : which 



like the anterior ones except that they abruptly bent 



near the distal end. Notopodial acicula are three or four delie 

 fibers which enter the base of the notocirrv.s. 



Setae are of vitct - -:ructure and all more or less yellow, the more 

 slender ones being very pale, the si nes The usual four 



kinds occur, but they present greater variati ind more transi:: 

 forms than usual. Articulated crochets ^Pl. XVII. figs. 61, 62 are 

 confined to the first eight parapodia. On the first three they occur 

 in an irregular, open, vertical, preacicular series of three j\ one 



or two on the acicular tubercle beneath the aciculum and on-. 

 acicular — about six or seven in all. On the fourth :': :■: V :iioseinthe 

 dorsal::, st | art . : the :..scicle are :. -.: le acute sel 



