1911.] NATURAL SCIENCES OF PHILADELPHIA. 249 



Peristomium very large, fully as long as the three succeeding seg- 

 ments and forming a prominent collar, into which the prostomium is 

 retracted, most deeply in the larger specimens; on each side a shallow 

 notch, below which it is produced forward more prominently to form 

 a slightly crenulated lower lip with concave border. Somite II also 

 apodous, not exceeding one-third length of peristomium with which 

 it is coalesced at the sides. Nuchal qirri similar to cephalic tentacles 

 but more slender, reaching to or nearly to the cephalic border of 

 the prostomium. Metastomial podous segments well-defined, very 

 regular, simple, 10-14 times as wide as long anteriorly, not over 8 

 times as wide as long posteriorly, strongly arched above, flattened, 

 with neural furrow below. They increase in width gradually to about 

 XL, then taper gently caudad. 



Pygidium a short ring with a slight marginal thickening and bearing 

 a pair of slender, little-tapered, stiff and smooth cirri as long as the 

 last six segments and arising close together below the large anus. 

 Immediately below and concealed by these is a second pair of minute 

 and inconspicuous cirri. 



Parapodia (PI. XV, fig. 20) of simple form and exhibiting the 

 changes in position and proportions usual in the genus. Notocirri 

 four or five, or posteriorly (where the parapodia become shortened) 

 even more, times as long as the neuropodia, slightly tapered and 

 smooth or very slightly wrinkled, becoming much more slender pos- 

 teriorly. Neurocirri prominent anteriorly, with thick, swollen, ovate 

 bases and short, thick, cylindroid styles. Farther back the basal 

 part is gradually reduced and finally becomes minute and the style 

 becomes first short and conical and then slender and tapered, but 

 always considerably exceeds the neuropodium in length. 



Acicula all very dark brown and opake except that the tips are 

 often pale; the neuropodial three or anteriorly sometimes two, pro- 

 jecting from the acicular tubercle at the dorsal level of the fascicle of 

 simple setre. They are simple, tapering rods with rathei acute points 

 on anterior parapodia and blunt, often bent or somewhat knobbed 

 ends on posterior parapodia where they become very stout. Noto- 

 podial acicula'a fascicle of slender brown fibers passing into the base 

 of the notocirrus in connection with a heavy mass of brown pigment. 



With the exception of the stout crochets which are brown, the setae 

 are colorless or pale yellow. Three kinds occur on all segments. Simple, 

 slender, wingless capillary seta? form a small dorsal tuft in connection 

 with the acicula. Among the bases of the capillary sets? are delicate 

 pectinate setae with slightly curved ends provided with a few indistinct 

 17 



