50 U.S. NATIONAL MUSEUM BULLETIN 227 



falcigers, fig. 10c?); (3) a group of compound setae arranged anterior 

 and ventral to group (2), with slender shafts, with terminal blades 

 long, slender, sometimes pseudoarticulated, with fine bifid hooked tips. 



Key to the New England Species of Sthenelais 



1. Anterior elytra with simple and bifid fringe on external border (fig. lie); 

 middle (after segment 12 or so) and posterior elytra without fringe but with 

 a deep notch on the external side (fig. lid) ; elytra thin, translucent, delicate, 

 smooth, without microtubercles. Parapodial stylodes (fingerlike fringe of pa- 

 pillae on parapodial tips) of anterior segments long and prominent (fig. lie). 

 Middle group of neurosetae composed of only a few compound falcigers with 

 terminal blades short and with bifid hooked tips; most consist of compound 

 neurosetae with terminal blades tapering to pointed tips, with blades long 

 to short (compound spinigers ; longer blades may be pseudoarticulated) . 



S. limicola 



All elytra with simple fringe on external border, elytra thicker, opaque, with 



microtubercles. Parapodial stylodes short. Middle group of neurosetae 



composed of numerous stout compound falcigers, with terminal blades short 



and with bifid hooked tips (fig. lOd) S. boa 



Sthenelais boa (Johnston, 1833) 



Figure 10,a-d 



Sthenelais pida Verrill, 1881, pp. 291, 300, 317, 320, 321, pi. 6, fig. 7, pi. 7, fig. 3.— 

 Webster and Benedict, 1884, p. 701.— Wilson, 1900, p. 351.— Sumner, 

 Osburn, and Cole, 1913, p. 618. 



Sthenelais boa Fauvel, 1923, p. 110, fig. 41,a-?; 1933, p. 13; 1953, p. 61, fig. 28,a-A;; 

 1957a, p. 4.— Monro, 1933a, p. 246, fig. 1.— Wesenberg-Lund, 1949, p. 257.— 

 Day, 1953, p. 406; 1960, p. 289.— Tebble, 1955, p. 76.— Renaud, 1956, p. 6, 

 fig. 4.— Uschakov and Wu, 1959, p. 37.— Fauvel and Rullier, 1959, p. 503.— 

 Clark, 1960, p. 14. 



Sthenelais leidyi Hartman, 1942b, p. 30, figs. 36-39; 1945, p. 10; 1959a, p. 120.— 

 Pratt, 1951, p. 328.— Costello, et al., 1957, p. 98. 



Sthenelais articulata Hartman, 1951, p. 20. 



Description.— Length up to 200 mm., width including setae up to 

 5 mm., segments up to 200 or more. Elytra subreniform or broadly 

 lunate, with a deep emargination in center of anterior border. Com- 

 plete surface of anterior few elytra covered with microtubercles (smaU 

 rounded, slightly obtuse); on more posterior elytra, microtubercles 

 confined to anterior part and along lateral border. Color: elytra 

 variable in color, mottled greyish on inner part, forming a wide mid- 

 dorsal longitudinal band; irregularly mottled greyish on most of 

 elytra with darker brown on middorsal part; mottled with darker 

 bands on posterior and inner borders of elytra; sometimes with rusty 

 extraneous material on elytra and setae. 



Biology. — A rather sluggish form but can burrow with rapidity. 

 Found intertidally in sand, muddy sand, and in sand with gravel. 

 Dredged on silty sand and shelly bottom. Ripe individuals found 



