20 U.S. NATIONAL MUSEUM BULLETIN 22 7 



Description.- — Length up to 100 mm., width including setae up to 

 9 mm., segments up to 80. Body elongated, vermiform, greatly flat- 

 tened dorsoventrally. Elytra numerous pairs (30-50), continuing to 

 near posterior end, oval, smooth, lacking tubercles and fringes of 

 papillae, overlapping somewhat except medially where there may 

 be a middorsal strip uncovered. The arrangement of the elytra in 

 the posterior region is irregular, i.e., not always symmetrically paired, 

 and as many as 7 elytra in a row. The elytra of young specimens 

 have a peculiar conical raised area just medial to the elytrophores. 

 Notosetae few, delicate, capillary. Neurosetae stout, bidentate, 

 amber colored, the upper 1 or 2 stouter, darker and pointed. Color: 

 body darkly pigmented reddish purple to dark gray or black; dorsal 

 cirri with a dark subterminal band; elytra with small blotches of 

 gray to black pigment with a lighter spot near the elytrophore. 



BioLOGY.^ — Active crawler, usually confined to the intertidal 

 region, living commensally with other polychaetes, mostly terebellids. 

 Found on flats of muddy sand and coarse gravel with mud, in the 

 muddy tubes of the terebellid Amphitrite ornata Verrill (Massachu- 

 setts, Connecticut, New Jersey, Virginia, North Carolina), with the 

 onuphid Diopatra cuprea (Bosc) (Beaufort, North Carolina, A. S. 

 Pearse), with terebellid worms including Thelepus setosus (Quatrefages) 

 (Florida, Hartman, 1951). Found among oysters (South Carolina). 

 Shows some of the adaptations characteristic of polynoid tube- 

 dwelling commensals, such as melanistic pigmentation, smooth elytra, 

 extra heavy upper neurosetae which aid in crawling in the tube. 

 Smaller specimens found in the tubes of Amphitrite ornata (some 45 

 segments, 23 pairs of elytra, Barnstable, August 23, 1954, and Duxbury, 

 September 1, 1952). 



Material examined. — Numerous specimens from Massachusetts 

 (Annisquam River, Cape Ann, Duxbury, Barnstable, Wellfleet, Woods 

 Hole region), Virginia (York River), North Carolina (Beaufort), 

 South Carolina, Georgia (Sapelo Sound, 6-13 fathoms), and Florida, 

 in low water. 



Distribution. — Massachusetts (Cape Ann) to Florida and Gulf 

 of Mexico (Florida, Louisiana, Texas), Low water to 13 fathoms. 



Genus Alentiana Hartman, 1942b 



Type (original designation): Alentiana aurantiaca (Verrill, 1885a). 

 Contains only one New England species. 



Alentiana aurantiaca (Verrill, 1885a) 



Figure 4,f7-j 



Polynoe aurantiaca Verrill, 1885a, p. 525, pi. 40, fig. 173; 1885b, p. 425. 

 Alentiana aurantiaca Hartman, 1942b, p. 20, figs. 1-6. 



