NO. 3 HARTMAN : ORBINIIDAE, APISTOBRANCHIDAE, PARAONIDAE 3 1 7 



Aricidea fragilis Webster, 1879 

 Plate 43, fig. 3 



Aricidea fragilis Webster, 1879, pp. 255-257, pi. 9, figs. 127-132; Hart- 

 man, 1944d, pp. 315-316, pi. 27, figs. 4, 5; Hartman, 1945, pp. 

 8, 30, pi. 6, fig. 3. 

 Collections. — North Carolina, along shore (more than 50). 

 Individuals measure about 40 mm long and are attenuated in their 

 posterior part. The prostomium is depressed equitriangular, rounded in 

 front and has a pair of small eyespots; the median antenna is cirriform; 

 nuchal organs are slitlike at the posterior ectal margin. Branchiae are 

 first present from the fourth setigerous segment and number 50 to 60 

 pairs. Parapodia of branchial segments have a long cirriform notopodial 

 postsetal lobe with a basal enlargement; the corresponding neuropodial 

 postsetal lobe (or ventral cirrus) is largest in branchial segments and 

 disappears gradually in postbranchial segments. 



Setae in all anterior segments are long, slender and distally pointed. 

 Median and posterior abdominal notopodia have a long, slender and 

 threadlike postsetal lobe extending distally as far as the shortest ac- 

 companying setae, and a slender setal fascicle consisting of about 12 

 very slender capillary setae. The corresponding neuropodium has a long 

 low postsetal ridge and a full, fan-shaped fascicle of 30 to 40 setae in 

 which the longest are uppermost and there is gradual diminution farther 

 down. In median and posterior segments these neuropodial setae are 

 pseudoarticulate, with a distal, slenderer and tapering part weakly 

 separable from a longer shaft (fig. 3). Breakage is most frequent at 

 this region and may result in a setae that appears distally bifid, with the 

 side opposite the cutting edge resembling a distal arista. There is a 

 visible pubescence on the outer side of the seta at the pseudoarticulate 

 region. The anal end terminates in a collarlike segment with three cirri- 

 form processes. 



Aricidea fragilis, sensu Fauvel (1936, p. 65), from Morocco, is be- 

 lieved to be a different species because the modified neuropodial setae are 

 hooked and have a terminal hood ; it is here renamed Aricidea fauveli 

 (see below). Aricidea fragilis Mcintosh (1885, pp. 354-355), from off 

 New York in 1340 fathoms, is very doubtfully the same because of its 

 abyssal occurrence. 



Distribution. — Aricidea fragilis Webster as defined herein is believed 

 to occur only in intertidal sandy shores of the eastern United States. 



