Boone, Arinelida, Cruises of "Alva" 95 



ably gradually from the first to seventh anterior segments and 

 similarly decrease in size caudad as usual. The neurocirri are very 

 nearly uniform throughout the somites, those of the third to ninth 

 anterior segments being very little smaller than those of the suc- 

 cessive segments. Each neurocirrus has a rather fleshy thick 

 basal portion completed by a distinctly defined, conic distal finger- 

 like article. 



The pectinate setae occur with a fair regularity from the 

 twenty-seventh somite onward on alternate somites. Each pecti- 

 nate setum is ventral in position on the parapodium to the setae 

 cluster and acicule, and has its distal end unequally dilated, so that 

 the distal subcircular face is readily applied as a grasper to the 

 surface of the coral rock ; this subcircular face of the pectinate 

 setum is cut into a series of rough, rounded nodes (giving a minia- 

 ture cobble-stoned effect) . 



The ventral acicule is next above the pectinate setum. The 

 acicula are visible externally from the third somite on, caudad, 

 the fourth somite shows the tips of both the dorsal and ventral 

 acicula as do also the succeeding segments. The visible portions 

 of the acicula are short, projecting only for a short distance beyond 

 the parapodia and are basally yellowish, conical, tapered to a very 

 acuminate black tip, the acicula of the anterior somites lying in 

 close proximity, whereas farther back they are more separated, 

 one being dorsal and adjacent to the large tuft of setae and the 

 other similarly ventral. On the somites forming the anterior third 

 of the specimen the tip of the acicula are acuminate, but on the 

 somites of the median third, the hinder portion being absent, the 

 acicula have their tips corrugate into several coarse lobes, forming 

 two to three blunted teeth, as shown in figure e ; these teeth being 

 present especially toward the ventral side. All the acicula are 

 procurved forwards. 



The ventral or neural cluster of setae, adjacent to the ventral 

 acicule, are set in a cluster of three rows of about five setae each, 

 these rows being arranged cephalo-caudad in position ; the spines 

 of the anterior row being the longest of the series and these dis- 

 tinctly decreasing in length dorsad. The longest, or most ventral 

 setum, bears proximally an articulated spine on either side of the 

 base. This and all other setae of the series are procurved ventrally 

 and are composite. The distal articles of the composite setae are 

 figured in fig. d. The proximal joint or shaft is strong, distally 



