POLTCHAETE WORMS, PART 1 269 



3. Prostomium spatulate, flattened dorsoventrally, without eyes (fig. 72a). 



Maxillae symmetrical; maxillae I strongly falcate, with or without teeth 

 at base (fig. 72A) ; mandibles absent or poorly developed, wedge shaped 



(fig. 72.9) Drilonereis (p. 271) 



Prostomium conical, only slightly flattened ventrally, usually with 4 eyes on 

 posterior margin (fig. 73a). Maxillae I and II asymmetrical: maxillae I 

 dentate along entire length or only slightly falcate distally (fig. 73, f-g,i). 



Notocirrus (p. 275) 



4. Prostomium flattened, spatulate, without eyes. Mandibles absent. 



Drilonereis (p. 271) 



Prostomium conical, only slightly flattened, with 4 eyes on posterior margin; 



mandibles well developed, wing shaped Notocirrus (p. 275) 



Genus Arabella Griibe, 1850 



Type (original designation): Arabella guadristnata (Grube, 1840); 

 = Arabella tricolor (Montagu, 1804). Contains only one New Eng- 

 land species. 



Arabella iricolor (IMontagu, 1804) 



Figure 71,a-e 



Lumhriconereis opalina Verrill and Smith, 1874, pp. 26, 38, 48, 70, 77, 83, 103, 116, 

 134, 140, 174, 300, pi. 13, figs. 69-70. 



Arabella opalina Webster, 1879, p. 242; 1884, p. 321; 1886, p. 145.— Verrill, 1881, 

 pp. 291, 301, 317, 322, pi. 4, fig. 4.— Webster and Benedict, 1884, p. 721.— 

 Andrews, 1891a, p. 288.— Sumner, Osburn, and Cole, 1913, p. 622.— Tread- 

 well, in Cowles, 1930, p. 342. 



Aracoda semimaculata Moore, 1911, p. 295, pi. 20, figs. 143-149. 



Arabella iricolor Fauvel, 1923, p. 438, fig. 175,a-A; 1933, p. 37; 1953, p. 274, 

 fig. 140,a-/i; 1955, p. 8; 1957b, p. 214.— Annenkova, 1938, p. 169.— Hartman, 

 1942b, p. 55; 1944d, p. 173; 1945, p. 27; 1951, p. 63; 1956, pp. 247, 288.— 

 Berkeley and Berkeley, 1948, p. 97, figs. 147-149. — Hartman and Reish, 

 1950, p. 25.— Uschakov, 1955, p. 244, fig. 81.— Rioja, 1958, p. 269.— Fauvel 

 and Rullier, 1959, p. 950.— Clark, 1960, p. 24.— Wesenberg-Lund, 1962, p. 118. 



Arabella iricolor var. caerulea Day, 1953, p. 439, fig. 6n; 1960, p. 363. 



Description. — Length up to 600 mm., width up to 5 mm., segments 

 up to 500. Prostomium (fig. 71a) bluntly conical, flattened ventrally, 

 arched dorsall}^, with 4 small black e3^es in nearly transverse line on 

 posterior dorsal margin (prostomium may be contracted into buccal 

 segment, thus hiding the eyes). Eyes subequal or either outer or 

 inner pairs may be slightly larger. Parapodia (fig. 716) with short 

 rounded presetal lobe, with longer digitiform postsetal lobe, becoming 

 longer and more or less erect in middle and posterior segments. Setae 

 simple, limbate, curved, with fine tips; some strongly curved and 

 denticlcd at base of the winged plate (fig. 71c). Acicula yellow, 

 numerous, often terminating in capillary tips which may surpass the 

 setigerous lobe. Anal cirri 2 to 4, short (may be pau- of short dorsal 

 ones and pair of short ventral knobs). 



