148 U.S. NATIONAL MUSEUM BULLETIN 227 



Material examined. — Maine (between Barter and Hodgdon 

 Islands, Boothbay Harbor region), Massachusetts (Georges Bank; 

 Vineyard Sound; off Ram Island, Woods Hole, April 6 and 12, 1883, 

 V. N. Edwards, male stolon at sm-face; Eel Pond, Woods Hole, female 

 stolon -with egg sac, at sm-face, March 3, 1956, M. Gray). 



Distribution. — Scattered records in the Arctic. Also Iceland, 

 Labrador to North Carolina, Bering Sea to Washington. Low water 

 to 123.5 fathoms; sexual forms at surface. 



Family Nereidae ( = Lycoridae) 



Body usually elongate, cylindrical, attenuated posteriorly. Pro- 

 stomium distinct, suboval to subpyriform, with 4 eyes (rarely absent) , 

 2 frontal antennae, 2 biarticidated palps (fig. 45a). First or tentacu- 

 lar segment usually apodous and achaetous; tentacular cirri usually 

 4 pairs (rarely 3 pairs, as in Lycastopsis) . Except for the first 2 

 setigers, parapodia usually biramous (uniramous in some, as Ly- 

 castopsis), with dorsal and ventral cirri, with varying degrees of de- 

 velopment of extra tonguelike extensions or ligules. Setae usually 

 compound spinigers and falcigers. Pygidium with pair of anal cirri. 



Proboscis (fig. 45,c-e) strong, muscular, eversible, differentiated into 

 oral (proximal) and maxillary (distal) rings, terminating distally in 

 a pair of horny falcate jaws that are toothed along the concave edge. 

 The areas on the maxillary ring are, by convention, numbered from 

 I to IV (dorsal median group i, 2 dorsolaterals ii, ventral median 

 III, 2 ventrolaterals iv), those of the oral ring v-viii (median 

 dorsal v, 2 dorsolaterals vi, median ventral vii, 2 ventrolaterals 

 VIII, vii-viii more or less continuous) . 



The areas of the proboscis may be naked or provided with soft 

 papillae (as in Ceratocephale, fig. 42a), small comblike denticles or 

 pectinae (as in Platynereis, fig. 43,/,^), or conical horny denticles or 

 paragnaths (as in Nereis, fig. 45,c-e). The proboscis or pharynx is 

 often everted or may be readily observed by a short incision near 

 the midventral line of the tentacular segment. 



At maturity, many nereids undergo a Idnd of metamorphosis, 

 undergoing profound structural modifications, referred to as the 

 epitokous phase or heteronereis stage. They become much better 

 swimmers than the atokous or nereid form and may become pelagic 

 when discharging their sex products. Epitoky varies from only 

 slightly modified swarm ers to sexually dimorphic male and female 

 heteronereids in which the body goes through marked changes, such 

 as: the eyes become extremely enlarged and may cause marked 

 changes in the shape of the prostomium, and usually associated with 

 greater sensitivity to light; body divides into 2-3 distinct regions. 



