POLYCHAETE WORMS, PART 1 171 



Notosetoe consist of homogomph spinigers. Upper bundle of 

 neurosetae consist of liomogomph spinigers and heterogomph falcigers 

 with long blades; lower bundle of neurosetae consist of heterogomph 

 spinigers and falcigers with long blades. Neuropodial heterogomph 

 falcigers usually absent in tlic middle and posterior segments (may- 

 be present throughout in young specimens). Proboscis with black 

 to dark amber-colored jaws, each with 5-10 teeth. 



Paragnaths variable in color, number, size and arrangement; they 

 may be black to light amber colored, rarely represented by papillae 

 only on some areas. There may be several small paragnaths instead 

 of a single large one. They may be conical, pointed to low, flat. 

 Area i with 0-7 denticles; area ii, arched groups (1-8); area iii, 

 irregular transverse group of 2-3 irregular rows (4-14); area iv, 

 arched groups (5-27); area v, 0-4; area vi, 0-5; areas vii-viii, 

 irregular transverse band of 2-3 irregular rows. 



Color, in life: iridescent greenish to bluish, with or without golden 

 yellow or red spots scattered along middorsal line and on parapodia, 

 some with whitish spots; greenish brown with scattered opaque 

 whitish spots, more concentrated along prostomium and middorsal 

 line; dark brown, cupreous. 



The mature sexual forms develop into a slightly modified hetero- 

 nereis. The ej^es become slightly larger and more bulging. The 

 first 7 pairs of dorsal cirri become cylindrical with curved tips (on 

 males only?), the first 5 pairs of ventral cirri become slightly modified. 

 The anal segment becomes crenulate. The body is not sharply set 

 off into regions although the segments are more compressed in pos- 

 terior two-thirds of body, and the parapodia are provided with a 

 modified type of swimming setae in addition to the normal type of 

 setae, i.e., they do not replace the normal type of setae, as in a well 

 developed type of heteronereis. The swimming setae have a flattened 

 blade, tapering abruptly to a short pointed tip. In the larger form 

 swarming at the surface (270 mm. long, 25 mm. wide, 148 segments, 

 Cape Cod Canal, Massachusetts, May 2 and 17, 1954), the parapodial 

 lobes, especially the large upper dorsal ligules, start enlarging around 

 segment 22, gradually enlarge to the middle of the body, then decrease 

 gradually in size; the paragnaths on the proboscis were degenerate, 

 mostly just amber-colored spots indicating the areas of the paragnaths. 



Biology. — Nereis virens, commonly known as "clam worm" or 

 "sandworm," is found in the sheltered shores of both sounds and 

 estuaries, burrowing near the low water mark of the sandy and muddy 

 shores and consideral)le distance farther up, where it ranges nearly 

 to the top of the high water mark. It is especially common in flats 

 bordering the mouths of rivers. It is found in all types of soils, in- 

 cluding coarse and fine muddy sand, gravelly sand, in clay, peat, in 



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