PLOTOIUA rONICEPS. 157 



the type protrudes conspicuously, presenting a disc-shaped base, on th(^ middle 

 of which is borne a cylindrical, flat-topped eminence. In a paratype from Sta. 

 4661 the retort-organ is not fully protruded, a fold of it extending out as a frill. 

 (Plate 66, fig. 2, 3). 



The second somite has an anterior division above more elevated and con- 

 tinuous with head. From the posterior surface of this portion the median lolje 

 projects caudad; it is somewhat conical, but is distally (caudally) rounded and 

 is a little flattened dorsoventrally. On each side of the median lobe the large 

 and conspicuous branchiform organ projects ectocaudad. Each presents two 

 principal divisions, a minor ectocephalic one, composed usually of three equal 

 lobes or filaments, and a major division which is pinnately branched, the branches 

 along each side of the principal stem sometimes showing slight secondary ones. 

 (Plate 66, fig. 2, 3). 



The somites in general are long, in the middle region of the body being fully 

 half as long as wide, the length greater in proportion to the width in the narrow 

 region. The somites, toward the sides especially, show usually four secondary 

 rings separated by sulci; these sulci are commonly less deep dorsally and ven- 

 trally. The parapodia arising on the most caudal ring of each somite. The 

 pygidium is short and is shaped somewhat like the frustrum of a cone, with the 

 caudal surface broad. Anal cirri lost. (Plate 66, fig. 4). 



While the styles of all cirri are lost, the cirrophores are prominent and show 

 the same arrangement as in the preceding species. A style found loose in a vial 

 with one specimen is broad, with the edge evenly rounded. There is a single 

 cirrus on each side of each of the first two postcephalic somites. On the others, 

 both notocirri and neurocirri are present above and below the setigerous tubercle. 

 The cirri on each somite on each side are widely separated, arising from opposite 

 ends of a common elevation, on the middle of which the setigerous lobe arises 

 as a low conical eminence. The setae in each parapodium are two in number, 

 one on each side of the aciculum, as usual. They are colorless, evenly moder- 

 ately curved, and prominent. 



Localities. Off Peru: Sta. 4661 (lat. 10° 17' S., long. 88° 02' W.). Sur- 

 face. Surface temp. 69° F. 15 November, 1904. One specimen. 



Off Peru: Sta. 4671 (lat. 12° 07' S., long. 78° 28' W.). Surface temp. 66° F. 

 20 November, 1904. One specimen taken at surface. 



Off Peru: Sta. 4675 (lat. 12° 54' S., long. 78° 33' W.). 300 fms. to surface. 

 Surface temp. 68° F. One rubbed specimen, probably this species. 



Southwest of the Galapagos: Sta. 4717 (lat. 5° 11' S., long. 98° 56' W.). 



