146 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 22 



Praxillella trifila, new species 

 (Plate 15, figs. 2, 4) 

 Praxillella, unknown sp. Hartman and Barnard, this volume, p. 46. 



The type is chosen from San Nicolas Basin (Sta. 6341) ; others are 

 from Santa Catalina and San Nicolas Basins. All are fragmented, repre- 

 sented by slender pieces with large, nodular segmental nodes, and cylin- 

 drical, arenaceous tube fragments. Length of a longer posterior end, with 

 1 1 setigerous segments and an anal cone, is 28 mm and width 1 mm. 

 Segments probably total 19 on complete specimens. The cephalic plaque 

 is plain, with a small triangular prostomial lobe lacking eyes, separated 

 from the lateral flanges by a pair of anterolateral incisions, and continued 

 middorsally to a median incision. The nuchal organs are parallel, straight 

 grooves extending through most of the length of the cephalic plaque. 



The peristomium is about two and a half times as long as wide ; it is 

 separated from the first setigerous segment by a faint segmental line. The 

 first 3 setigerous segments are long, cylindrical, their length about 5 

 times their width. Each has long, slender, distally pointed setae in noto- 

 podia, and single, acicular spines in neuropodia. The third neuropodium 

 usually has 2 spines on a side. From the fourth segment the length/width 

 ratio is 2/1 or less. These segments have neuropodia provided with 

 rostrate hooks (Plate 15, fig. 4) in vertical series. 



The body terminates in a long cone with terminal pore. In some the 

 proctodaeum is everted as a subspherical sack (Plate 15, fig. 2) ; in 

 others it is withdrawn. The cone is characterized by the presence of 3 

 very long, slender cirri, a pair in dorsolateral, and a midventral attach- 

 ment. This cone is preceded by 3 long, barrel-shaped asetigerous seg- 

 ments, and a fourth in which rostrate hooks (Plate 15, fig. 4) are present 

 in sparse numbers, and also one or a few very slender pointed setae. The 

 fourth preanal segment is imperfectly setigerous. 



Praxillella trifila is characterized by having 3 very long, slender cirri 

 on the anal cone; segments lack a collar; the first 3 setigerous segments 

 have acicular spines. It bears a resemblance to Asychis trifilosa Augener 

 (1926, p. 187; Mesnil and Fauvel, 1939, fig. 12) from New Zealand 

 and the Gulf of Oman in deep water, which also has 3 long anal cirri ; 

 the latter, however, has a collar on the fifth segment. 



P. trifila has been recovered only in deeper parts of the middle and 

 outer basins; it is believed to be a deep water form. 



