NEREIS CAENOCIRRUS. 211 



cirri the parapodia form two sharply defined groups. In the first, embracing 

 the first seven pairs, the style of the notocirri from a constricted base expands 

 into a conspicuously large body, from the distal end of which extends a very 

 slender tapered process, like a slender beak from a bird's head. In the second 

 group, embracing the eighth to fifteenth pairs, the notocirri are of the ordinary 

 form; slenderly uniformly tapered from the base distad. The notocirri of the 

 most anterior parapodia of the nereid division are attached near the distal end; 

 caudad the point of attachment shifts farther proximad and in the last ones is 

 near the middle of the notopodium. As to the character of the neurocirri there 

 are also two groups. The first of these embraces the first five pairs in which 

 the form is very similar to that of the anterior notocirri, presenting a large 

 expanded middle body, from the distal end of which a very slender, short, obUque 

 distal process extends. On the succeeding parapodia they have the usual slender, 

 distally attenuated form, and decrease somewhat toward the caudal region. 

 The first of this group are broader proximally and somewhat flattened. All 

 neurocirri attached near the base. The natatory parapodia of the heteronereid 

 division present the usual general differences from the others, being as a whole 

 longer, deeper, and much flattened in the anterocaudal direction, and bearing 

 large and conspicuous foliaceous developments. The notopodium bears two of 

 these thin, finely veined, transparent appendages. One on the dorsal side, 

 attached near the notocirrus, is slenderly lanceolate and does not attain the ends 

 of the shafts ot the setae. The other is attached on the ventral side, is much 

 larger, and presents the usual auricle proximally on the ventral side of the neu- 

 ropodium, well proximad of the distal end. It is symmetrically pointed distad 

 and is abruptly narrower just below its middle. From the distal end of the 

 neuropodium arises a very large, subcordate appendage, distally well rounded, 

 with a rather narrow, curved, auricular appendage on the dorsal side at base. 

 The notocirrus bears on the dorsal side of its base a subelliptic foliaceous body 

 attached by one side; the style itself is about equal in length to the cirri; below 

 a slender, transparent, smooth tip there is along the side toward the setae a series 

 of unusually long, well separated and conspicuous enlargements. The nem'o- 

 cirrus presents a short, thick cirrophore, from which rises a style of the ordinary 

 sort and two membranous appendages, a narrowly oblong, weakly sigmoid one 

 on the distal side of the style and, on the proximal side, a much larger one of 

 subdeltoid outline. In the caudal region the same parts are present, but become 

 much smaller. Apparently in the last three pairs the foliaceous appendages 

 are aU lacking, the styles of the cirri being long and conspicuous, with the other 



