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U.S. NATIONAL MUSEUM BULLETIN 2 27 



of the body. Notopodium with 2 subequal, triangular to conical lig- 

 ules, gradually tapering to a broad tip. Neuropodium with conical 

 setigerous lobe and a lower ligule similar to the notopodial ligules. Dor- 

 sal cirri longer than the ligules; ventral cirri equal to or slightly shorter 

 than the ligules. 



In the anterior region, notosetae consist of homogomph spinigers. 

 Upper group of neurosetae, homogomph spinigers and heterogomph 

 falcigers; lower group of neurosetae, heterogomph spinigers and fal- 

 cigers with rather short blades. In the middle and posterior regions, 

 notosetae consist of few (1-3 or so) homogomph falcigers with short, 

 blunt oval blades (begin on about setiger 30). Neurosetae similar 

 to anterior region except some of the heterogomph falcigers may lose 

 their blades and give the appearance of simple setae. Acicula black. 

 Proboscis with falcate jaws, each with 6-7 teeth; with paragnaths: 

 area i with 0-1 denticles; areas ii and iv, arched masses of 2-3 rows; 

 area iii, small transverse group of 2-3 rows; area v, (rarely 1); 

 area vi, oval mass (6-10 or more); areas vii-viii, a row of quite 

 large paragnaths (7-9) anterior to a wide band of small subequal ones. 



Color: faint to dark wide transverse bands of reddish, rusty brown, 

 violet, purple red (anterior fourth of segment without color) ; or with- 

 out color on smaller specimens. 



At maturity, sexually dimorphic heteronereids are formed. The 

 eyes are greatly enlarged. The body is divided into two regions, an 

 anterior region with the usual type of setae, and a posterior region with 

 the usual type of setae replaced by swimming setae, with segments 

 compressed and flattened anteroposteriorly, with extra development of 

 lamellar plates on neuropodia and bases of dorsal and ventral cirri. 

 Table 4 below shows how the sexually dimorphic males and females 

 differ. 



Table 4. — Differences between sexually dimorphic males and females of N. zonata 



