286 PROCEEDINGS OF THE ACADEMY OP [April, 



are elongated and directed forward, becoming in both respects less 

 so from before backward; on II and III they are remarkably slender 

 and silky and project far in front of the head to a distance of more 

 than twice the diameter of the body; those of V scarcely equal the 

 body diameter. On middle segments the fascicles spread more 

 widely over the dorsum and scarcely exceed the length of their seg- 

 ments. Posteriorly they appear relatively but not actually longer. 

 Neuropodial setse are slightly coarser and fewer than the corresponding 

 notopodials; those of the first three fascicles have filamentous tips 

 and project forward like the notopodials, but are only about half as 

 long; on other segments they curve dorsad up the sides of the body. 



Setse are all pale brown, soft and iridescent. As long as they project 

 forward notopodials and neuropodials are similar, excessively slender, 

 with straight acute tips and numerous cross fractures or nodes, which 

 at the base of fully-grown setae occur five or six in a distance equal to the 

 diameter, becoming gradually fewer until they are six or eight times as 

 far apart. As they lose the filamentous tips the notopodial setse have 

 the region of crowded joints toward the base much restricted (PI. IX, 

 fig. 61). 



Neuropodial seta? in becoming shorter and stouter also acquire fewer 

 and much longer joints, the terminal one becoming especially long 

 and, beginning with V, with a distinctly hooked tip, which a few seg- 

 ments farther back becomes much larger and provided with an acces- 

 sory process (fig. 60), thus having the form of a halter-snap like the 

 setse seen in certain species of Sthenelais. 



Color deep buff -gray and nearly uniform. 



Type locality, San Diego Bay, Cal., between tide limits. 

 Flabelligera commensalis sp. nov. (Plate IX, figs. 62, 63). 



Form moderately slender, thickest in the cephalic fourth, thence 

 tapering to caudal end but usually exhibiting irregular contractions 

 or swellings ; more or less distinctly prismatic and somewhat compressed ; 

 body-walls thin and delicate and more or less ruptured so that the 

 viscera protrude. Type and largest complete specimen 50 mm. long 

 and at the widest part (XX) 2.4 mm. wide and 3.2 mm. deep; this 

 thickness, however, is probably in part due to an abnormal swelling. 

 Number of somites 90; a second complete specimen 48 mm. long has 

 70 segments. 



Prostomium with its appendages capable of complete retraction 

 within the collar and only incompletely exposed in these specimens. 

 So far as observed it consists of a pair of thin membranous dorsal 

 lobes, each bearing a dense tuft of thirty or forty slender tentacular 



