86 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 25 



Family PARAONIDAE 



Genus Paraonis Grube, 1872 



Type P. tenera Grube, 1872 



Paraonis platybranchia, new species 



Collections. VELERO IV Station 6421 (7). 



This is a long, slender species. Length is about 15 mm, width 0.3 

 mm, segments number about 65-75. The prostomium and prebranchial 

 segments are pale ; the postbranchial segments are dull green, and the 

 posteriormost segments are again pale. The prostomium is prolonged 

 forward and acutely pointed ; it is longer than wide and broadest in its 

 ocular area. Eyes consist of 2 small black spots, one on either side near 

 the postectal margin of the prostomium. The first segment or peristomium 

 is poorly marked off from the prostomium and best seen ventrally be- 

 cause of the deep, midventral, longitudinal notch forming the lower 

 lip. This is followed by 3 setigerous segments having biramous setigerous 

 parapodia without branchiae. The setal fascicles of these segments are 

 lateral ; the individual setae are long, slender and hairlike. 



Branchiae are first present from the fourth setigerous segment and 

 continue posteriorly on 25 to 29 segments. Branchiae are broad, strap- 

 like and taper distally; all are about equally large, or the anterior and 

 posteriormost are gradually smaller; they are directed upward so that 

 the 2 of a pair nearly meet middorsally. 



Parapodia are most conspicuous because of the long, very slender 

 notopodial, postsetal lobe ; this extends distally to half of the free length 

 of the setae. These slender lobes continue throughout the length of the 

 body. The corresponding neuropodial parts lack these slender lobes. 

 Setae are all of one kind, slender, hairlike, and thus differ from those of 

 other known species of Paraonis (see Hartman, 1957, p. 329). 



The posterior end of the body terminates in a flat, auricular, ventral 

 lobe, about twice as wide as the last few segments; a pair of slender, 

 cirriform processes is attached on the dorsal side of the flat lobe. The 

 anal pore is on the dorsal side, behind the last body segment. 



Paraonis platybranchia has been found only at one station, taken 0.3 

 mi from near the United States-Mexican border, at latitude 32° 32' 00" 

 north, longitude 117° 07' 30" west, in a depth of 18 ft, in sediments 

 of coarse gray sand. The species was associated with Prionospio malm- 

 greni Claparede, Dispio uncinata Hartman, Nephtys caecoides Hartman, 

 and an Eteone sp. 



