1905.] NATURAL SCIENCES OF PHILADELPHIA. 533 



Parapodia are of the usual form and the two divisions are separated 

 by a broad naked achsetous space. All three cirri and the branches of 

 the gills (fig. 12) are long, slender and regularly tapering, the latter 

 shorter and more slender than the former. The cirri stand a little 

 anterior to the branchiferous zone, the dorsal a little medial to the first 

 dorsal gill, the ventral just behind the neuropodial setce and the middle 

 about halfway between. Usually the dorsal cirrus is somewhat longer 

 than the others. On most of the somites the branchiae number 7 or 6 

 pairs, 2 of which usually occur between the dorsal and middle cirri and 

 5 between the latter and the ventral margin of the notopodial setigerous 

 area. As the latter distance is much the shorter the gills occupying 

 it are much more crowded than those dorsal to the middle cirrus. 

 When but 6 gills are present the missing one is almost invariably the 

 second from the dorsal end. No gills occupy the smooth achsetous 

 interramal space as in some species. Individual branchiae are usually 

 biramous and cleft almost to the base; others have 3 branches, in 

 which case one is usually very much shorter than the other two; or 

 they may be simple and cirriform. 



The setae are all glistening white or colorless, giving to these worms a 

 beautiful silvery aspect. They are also extremely long, and as the 

 worms roll up they give the aspect of bristly balls like chestnut burrs 

 or minute porcupines. Those on the dorsal surface are much the longer 

 and conceal the cirri and branchiae completely from view. In the noto- 

 podial palisade the setse are disposed in about 4 transverse rows. In 

 the second row, counting from the anterior, are found the deeply cleft 

 serrate setse (fig. 11), but these appear to rarely extend much dorsad 

 of the middle cirrus. The prongs are slender and their inner margins 

 extensively and prominently serrated. Like other setae they are 

 hollow, with granular contents impregnated with calcium carbonate. 

 The first, third and fourth rows contain only the unequally pronged 

 bifid setae, those of the third row (fig. 9), while not much stouter, being 

 nearly twice as long as the others (fig. 10), and having much longer 

 prongs. As is the case with the serrate setae, the longer prong is ex- 

 panded slightly opposite the tip of the shorter, beyond which it tapers 

 in a slightly curved point. Neuropodial setae (fig. 8) have the form of 

 the smooth notopodials, and the longest are about the length of the 

 shorter of the latter. At the ventral margin of the bundles they be- 

 come much shorter with more strongly curved tips. Dried prepara- 

 tions of the smooth setae show that their cavities are camerated, with 

 septa and telescoped siphuncle-like tubes much like a Nautilus shell, 

 but much less regularly. 



