14 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.27 



A complete individual in two pieces measures 32 mm long and 4 

 mm wide with parapodia, in median segments. The body is depressed 

 and resembles a species of Pilar gis (see below) because antennae and 

 cirri are very short; the median antenna is sometimes difficult to identify. 

 The surface epithelium is minutely papillated; this is most obvious on 

 the dorsum, the superior edges of parapodia and the dorsal cirri. 



The prostomium (Fig. la) consists of a pair of subtriangular lobes, 

 each a little longer than wide, well separated in front and fused at the 

 base ; there are no visible eyes. The three antennae are short, digitate 

 and subequally short; each is about half as long as the prostomium; 

 they are inserted near the posterior margin of the head lobe, with the 

 laterals near the ectal margin and the median one where the prostomium 

 and first segment join. 



The first visible segment has a pair of short, subequal tentacular 

 cirri (Fig. la) ; each is longer than an antenna and slightly papillated, 

 seen only under magnification. The second segment, also without 

 parapodia and setae, has a similar dorsal, and a much shorter ventral 

 cirrus, resembling that of the third segment. The third segment, which 

 is the first setigerous, is the most reduced ; it has a small dorsal and 

 a smaller ventral cirrus, and its setal fascicle is inconspicuous. From 

 the fourth segment the parapodia are much larger and resemble those 

 of the fifth and successive segments. 



In typical parapodia the dorsal cirrophore encloses a slender aci- 

 culum or rod ; these enlarge in median and posterior segments to form 

 the conspicuous dorsal hooks. 'Fhey increase gradually in size and are 

 large, distally recurved, yellow crooked at about segment 18, (at seg- 

 ment 3, Redondo en, fan in 751 m) but are irregular in occurrence 

 through several segments. Where best developed (Fig. lb) in middle 

 and posterior segments, they emerge from the upper, basal edge of the 

 notopodium, well within the base of the dorsal cirrus. The accompanying 

 neuropodial setae (Fig. Ic) are much slenderer, nearly straight and di- 

 rected laterally; they number 4 to 7 in a fascicle, but are frequently 

 broken off near the base. 



Ancistrosyllis breviceps is allied to A. grocnlandica Mcintosh 

 (1879) (see Hartman, 1947, p. 497) from Greenland, in 410 fms, on 

 sandy mud. It also has small prostomial antennae, a papillated epithe- 

 lium and sharply crooklike notopodial hooks. The two differ in that 

 {\) A. breviceps lacks eyes, (2) the first large notopodial hooks are 

 first present at about segment 18 instead of far more anterior, (3) 

 the paired prostomial antennae are inserted more posterior in the first 

 than the second, (4) the dorsal cirri of the first setigerous segment 



