1911.] NATURAL SCIENCES OF PHILADELPHIA. 261 



rowed, terminating in a low, rounded acicular process and two broad, 

 flat lips, the post-acicular one being much the longer and truncate 

 distally. The short, simple notocirrus arises about the middle of its 

 dorsal face and barely reaches the distal end of the neuropodium. 

 Neurocirrus arises on ventral side close to mouth and fails to reach 

 the bases of the setae. Second parapodium (III) (fig. 42) is similar 

 but much smaller and both the post-acicular process (middle cirrus) 

 and notocirrus are much more slender and elongated, while the neuro- 

 cirrus is enlarged and bluntly conical. The third foot is of more normal 

 size and position and the notocirrus is still longer, reaching beyond the 

 postacicular lobe. But the chief change affects the neurocirrus, 

 which is no longer truly cirriform, but merely a small, rounded, cylin- 

 droid papillae. The fourth parapodium (fig. 43) differs only in the 

 complete suppression of the neurocirrus. After the fourth (somite V) 

 the neuropodia are gradually reduced in size until they become low, 

 compressed cones (fig. 44). The maximum size of the post-acicular 

 lobe is attained at about VII or VIII, after which it undergoes gradual 

 reduction, being still distinct at XV but obsolete at XXX. The 

 notocirrus retains its length longer, at its maximum reaching about 

 half-way to the middle line and exhibiting but little change until after 

 the appearance of the gills, when it becomes rapidly reduced to a 

 slender filament about one-third as long as the gill (fig. 44). Behind 

 IV the neurocirri become small, rounded glandular elevations which 

 gradually become smaller and finally disappear. 



Gills begin on XIV, though a small prophetic papillae occurs on 

 one side of XIII of one specimen. They arise at a brown vascular 

 knot on the dorsal side of the base of the notopodium, which, however, 

 is not so abruptly displaced ventrad as in Nothria pallida, though, 

 when the cirrus reaches its greatest reduction, it appears as little more 

 than a lateral process of the gill (fig. 44). From the first they equal 

 the notocirrus in length and seldom reach more than half-way to the 

 middle line. They have the usual form and structure but, unlike those 

 of N. iridescens and other species, become little flattened posteriorly. 



Neuropodial acicula four or five, stout, slightly curved and tapered, 

 the simply pointed tip apparently not reaching beyond the surface 

 on anterior parapodia. Farther back there are three with abruptly 

 tapered, acute, curved and often bent tips exposed for a short distance. 

 There are no evident notopodial acicula. 



Setae are of four kinds. Large setae on the anterior modified seg- 

 ments mostly broken, but several that are intact (PI. XVI, fig. 45) 

 are simple spines with the ends worn smooth as in Hyalincecia. A 



