272 PROCEEDINGS OF THE ACADEMY OF [April, 



The first six (V-X) with uncini in one row and having a length of 

 about twice the segment bearing them, the others with uncini in two 

 interlocking series and at first abruptly much longer, but the caudal 

 three or four again shorter and shifting on to the venter behind the 

 ventral plates. Abdominal tori small but prominent, latero- ventral 

 lappets bearing a single series of uncini sunken below a raised border 

 and terminating dorsally in a short cirrus-like projection. 



Setae pale yellow, numerous, arranged in two ranks in broad fas- 

 cicles, those of one rank shorter, but all rather long, tapered, acute, 

 bilimbate with rather broad but not extensive margins and entire, 

 unfringed tips. 



Uncini deep yellow on thorax, paler on abdomen. On first six 

 thoracic and all abdominal tori in a single series pointing forward, on 

 XI to XX in double interlocking series. About 40 on V to VII, 50 on 

 VIII-X, 80-85 on XI to XV and 50-60 on XVI to XX. Anterior 

 abdominal tori bear about 70 uncini. On somites V, VI and VII they 

 are large, with long tapered handle-like bases (PI. IX, fig. 45) and a 

 prominent anterior projection for muscular attachment; the beak is 

 long and nearly straight, the crest composed of a single transverse 

 series of large teeth and the guard large. These characters are most 

 pronounced on V and gradually decline on VI and VII. On VIII 

 to X the uncini are transitional to the typical form (PL IX, fig. 46), 

 which on the posterior thoracic somites has the manubrium much 

 reduced and chiefly replaced by a thin, translucent, ligamentous 

 expansion, the base short and triangular, the beak strongly hooked, 

 short and stout and the crest more elevated and composed of about 

 three transverse series of teeth of diminishing size. Abdominal 

 uncini (PL IX, fig. 47) still smaller with reduced convex bodies, acute, 

 strongly hooked beak, high crest composed of numerous teeth and 

 long filamentous anterior and posterior ligaments. 



Color in alcohol uniform dark brown. 



This species is founded on four specimens taken between tides at 

 San Diego by E. C. Starks. It differs from the Alaskan species pro- 

 visionally referred to P. fasciata in the much greater length and more 

 numerous abdominal segments, in the smaller lateral wings, the 

 absence of a post-branchial fold and especially in the form of the 

 branchiae. It is closely related to the Japanese species P. maculata 

 Marenzeller which has a similarly elongated body, three pairs of simi- 

 larly branched gills and uncini of similar form. The principal dis- 

 tinctions are that the latter has larger and more numerous ventral 

 plates and no distinct second pair of lateral wings. 



