1909.1 NATURAL SCIENCES OF PHILADELPHIA. 265 



what backwards to the mouth as a slightly rugous area; a few spots of 

 pigment but no distinct eyes on the dorsum. On each side at the 

 junction of prostomium and peristomium is a deep nuchal pit. 



Peristomium a distinct achaetous ring, longer than either prosto- 

 mium or somite II, simple and entire dorsally, but ventrally divided 

 nearly or quite to its posterior border by the large subtriangular mouth, 

 a small median process of II projecting slightly into the incision. 



Two regions of the body not sharply defined, distinguished chiefly 

 by differences in character of the notopodia and degree of develop- 

 ment of the gills. Segments of anterior region depressed, convex 

 below and flat above, distinct and sharply defined by well-marked 

 but not especially deep furrows, uniannular marked by a slight trans- 

 verse ridge ventrally and by a pair of faint impressed paramedian 

 longitudinal lines dorsally. Segments of posterior region short, at 

 first much crowded but farther back much less so, similar to those of 

 anterior region, but lacking the dorsal impressed lines and much more 

 strongly convex below. Caudal end depressed and broadly rounded, 

 ending in a short tubular pygidium with large anus directed slightly 

 upward and surrounded by a circle of papillae and a pair of minute 

 ventral cirri. 



Parapodia biramous, beginning on II and situated at a high level. 

 Neuropodia of anterior segments small, rather fleshy, elliptical sloping 

 prominences about as deep dorso-ventrally as long antero-posteriorly, 

 and produced into small rounded postsetal lobes which on more pos- 

 terior segments tend to be prolonged dorsad. They are largest on 

 the middle segments of the region and the three rows of stout setae 

 that they bear are here stoutest. Notopodia separated from neuro- 

 podia by a deep groove and consisting of small tubercles bearing 

 a slender tuft of capillary setae, behind and below which is a subcorneal, 

 erect postsetal lobe most prominent on anterior somites, and when 

 best developed bearing a convex wing on the ventral side of its base. 

 On posterior segments of this region the neuropodia become smaller 

 and shifted dorsad and the rami crowded. On the posterior region 

 both rami are borne on the dorsum and so closely approximated that 

 they seem almost to have a common somewhat elevated base. Both 

 rami are foliaceous, the neuropodium small and somewhat mammilli- 

 form bearing its setae in a fan-shaped fascicle; the notopodium con- 

 sisting of an erect, sub-lanceolate postsetal lobe and bearing a small 

 compact tuft of setae. 



Gills begin on from X to XII as slender, erect, conical processes on 

 the dorsum immediately above the notopodia. They undergo little 



