492 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



The original and only known account of this interesting species was 

 based on a small, incomplete individual only 20 mm long and 2 mm wide 

 from which posterior segments and pygidium were lacking. The several 

 individuals herein reported are considerably larger. A complete one 

 (preserved) with a regenerated posterior end, taken in Tomales Bay, 

 measures 200 mm long and consists of 460 segments, not counting the 

 closely crowded segments of the regenerated region. It is 4 mm wide 

 at its greatest width which is slightly behind the middle of the body. 

 Other individuals from San Francisco Bay are nearly as large and some 

 are posteriorly complete and normal. The body is broad, ribbonlike, 

 greatly depressed and proportionately very long for its width. Color in 

 alcohol is drab or gray but the conspicuous dorsal cirrophores are reddish 

 to dark brown. The dorsal side of the prostomium, antennae, palpi, and 

 peristomial and dorsal cirri, as also the entire dorsum of the body are 

 finely papillated (pi. 59). 



The prostomium consists of a pair of larger lateral lobes widely 

 separated from each other medially and a small, median, triangular 

 portion (pi. 59, fig. 1). The simple, club-shaped, paired antennae are 

 attached to the distal ends of the paired lobes. The separation between 

 prostomium and palpi can be discerned as a shallow groove under favor- 

 able lighting conditions. The large palpi project beneath and in front of 

 the prostomial lobes. They are separated from each other medially for 

 about half their length. Each consists of a thick, massive palpophore and 

 a tiny, distal palpostyle that is most clearly seen in ventral view (pi. 59, 

 fig. 2) . On the ventral side the palpi can be seen to extend posteriorly to 

 the oral aperture and peristomium. 



The peristomium or first ring is nearly as long as the next segment but 

 somewhat narrower. On the dorsal side it has a shallow median emargin- 

 ation where it joins the prostomium. On the ventral side its anterior 

 margin forms the lower lip and is slightly papillated. At the sides it is 

 provided with 2 pairs of fusiform, papillated tentacular cirri that exceed 

 the prostomial antennae in size. The dorsal ones are the larger. At the 

 anterior dorsal base of the tentacular cirri there is a small, fleshy elevation 

 visible in both dorsal and ventral views; these paired elevations are 

 larger than the epithelial papillae. 



The proboscis (everted in one individual) is soft, epithelial, trans- 

 lucent, delicate in texture and more or less globular in shape. In another 

 individual where the proboscis is retracted, by dissection it is seen to lie 



