108 U.S. NATIONAL IMUSEUM BULLETIN 2 27 



Biology. — Found at low water, under stones, in crevices of rocks, 

 in holdfasts of algae (as Laminaria) , among oysters. Dredged on 

 bottoms of coarse to fine sand, mud, silt, rocks, gravel, with old shells, 

 and serpuHd tubes. The early development has been followed by 

 Banse (1956). The reproductive period begins in early summer, the 

 larvae becoming important in the autumn plankton (in the Oersund, 

 they belong to the 4 most abundant larvae of the errant polychaetes, 

 see Thorson, 1946, as Eteone barbata, p. 62, fig. 27; see also Banse, 

 1956). The eggs are large and yolky and develop into yolky, drop- 

 shaped, rather undifferentiated larvae which s\^dm with the aid of a 

 prototroch. The larvae of 7-8 segments sink to the bottom. The 

 young stages develop a transitory unpaired prostomial antenna be- 

 tween the eyes; also the second and third tentacular segments develop 

 transitory setae. In the yomig of 18 segments, the parapodia show 

 the characteristic form of the adult. 



Material examined. — Type of Castalia cincinnata Verrill from 

 off Chesapeake Bay. Also off Newfoundland, Gulf of St. Lawrence, 

 Massachusetts, Rhode Island, North Carolina, 16 to 1,290 fathoms. 



Distribution. — Arctic, Bering Sea, Iceland, Norway to western 

 Baltic, France, Azores, Hudson Bay, off Newfoundland to off North 

 Carolina. Low water to 1,290 fathoms. 



Genus Parahesione Pettibone, 1956b 



Type (original designation): Parahesione luteola (Webster, 1880). 

 Contains only one New England species. 



Parahesione luteola (Webster, 1880) 



FiGUKE 29 



Hesione agilis Webster and Benedict, 1884, p. 707, pi. 1, figs. 9-11. 

 Podarke Ivieola Webster, 18S6, p. 135, pi. 5, figs. 19-20. 

 Parahesione luteola Pettibone, 1956b, p. 281, fig. l,a-c. 



Description. — Length up to 15 mm., width including setae up to 

 4 mm., segments up to 45. Body widest in middle, tapering gradually 

 anteriorly and posteriorly, flattened dorsoventrally. A single ten- 

 tacular segment visible dorsally, the 6 pairs of tentacular cutI crowded, 

 lateral to prostomium (fig. 29a) . Tentacular cu-ri long, slender, some 

 longer than dorsal cirri, upper ones longer than lower ones. Notopodia 

 a stout papilla below the cirrophore of the dorsal cirrus, with close- 

 set bundle of numerous capillary notosetae (fig. 29c). Neuropodia 

 stout, elongate, diagonally truncate. Neurosetae compound, with 

 terminal blades long to short. Dorsal cirri longer than setae, ar- 

 ticulated. Proboscis with a larger basal portion and narrower distal 

 portion, with numerous fine papillae around opening. Color, in 

 life: colorless or reddish yellow; preserved: greenish. 



