POLYCHAETE WORMS, PART 1 303 



Genus Aricidea Webster, 1879 



Type (monotypy): Aricidea fmgilis Webster, 1879. 



The species represented have the body slender, cjdindrical, more 

 or less flattened anteriorly. Prostomium rounded anteriorly, wider 

 and convex on posterior half, with a median antenna in about the 

 middle of the prostomium (rarely missing, indicated by a scar or low 

 ceratophore), with a pair of nuchal organs or slits which may be 

 darkly pigmented. Achaetous buccal segment more or less fused with 

 prostomium and ventrally forming lateral lips of mouth. First 2 

 segments forming a lobulated lower or posterior lip. Branchiae begin 

 on setiger 4, turned posteromedially on dorsum, ciliated. Notopodia 

 and neuropodia with thick bundles of capillary setae in anterior region 

 (fig. 80c). Notopodia with only capillary setae, without acicular setae 

 (subgenus Aricidea, sensu stricto). Notopodial postsetal lobes short, 

 conical in prebranchial segments; longer, digitiform, wider basally in 

 branchial segments; more delicate, filiform m postbranchial segments. 

 Where observed, anal end with 3 short slender anal cirri, 2 laterovcntral 

 ones longer, medioventral one shorter. 



Key to the New England Species of Aricidea 



1. Median antenna long, filiform, extending to about setigers 4-6 (fig. 80h). 



Postbranchial segments with 1 to few S-shaped neuropodial crotchets 



(fig. SOi). Branchiae 9-10 pairs A. (Aricidea) quadrilobata 



Median antenna short, extending at most to setiger 2 (fig. 80a). Post- 

 branchial segments without S-shaped neuropodial crotchets 2 



2. Posterior parapodia with neurosetae all capillaries (fig. 81/). With distinct 



conical postsetal neuropodial lobes on first setiger (fig. 81,b,d), low rounded 

 lobes on following 20 or so setigers (fig. 81e), absent from following. 



Branchiae 26-30 pairs A. (Aricidea) albatrossae 



Posterior parapodia with neurosetae of 2 kinds: (1) Long, slender, capillary; 

 (2) shorter, stouter (fig. 80d). Without distinct postsetal neuropodial lobes 

 on first setiger. Branchiae 10-24 pairs 3 



3. Posterior parapodia with stouter neuropodial hooked crotchets, hooded or with 



faint sheath (fig. 80c). Usually darkly pigmented. 



A. (Aricidea) jefiTreysii 

 Posterior parapodia with stouter neurosetae straight or slightly curved, with 

 terminal mucronate tips (fig. 80^). Whitish (not darkly pigmented). 



A. (Aricidea) suecica 



Aricidea {Aricidea) quadrilobata Webster and Benedict, 1887 



Figure 80,h,i 

 Aricidea quadrilobata Webster and Benedict, 1887, p. 739, pi. 8, figs. 93-96. 



Description. — Length up to 6 mm., width up to 0.6 mm., segments 

 about 100. Branchiae 9-10 pairs, broad at base, abruptly pointed 

 distally (fig. 80A). Notosetae of posterior segments long, fine, 

 capillary, forming spreading bundles, sometimes spreading out and 



