150 PROCEEDESTGS OF THE NATIONAL MUSEUAi vol. 117 



Euchone trisegmentata, new species 



Figure 3 



Material: Station 5(7). 



Description: All specimens complete, measured 5-7 mm. long, 

 including the tentacles, and 0.3 mm. wide. All have 8 thoracic and 

 9 abdominal segments; the last 3 abdominal segments comprise the 

 anal depression (fig. 3a) . Two specimens contained ova in the coelom. 

 Branchial crown with 3 pinnate radioles per side, each radiole with 

 numerous filaments and united by a membrane for % of their length. 

 Collar little developed dorsally but is produced centrally into two lobes. 



Thoracic notopodia composed of superior single-winged capillary 

 setae (fig. 46) and inferior subspatulate setae (fig. 4c). Thoracic 

 neuropodial long-handled uncini provided with a large tooth and six 

 smaller ones (fig. 4d). 



Anterior abdominal notopodia with acicular hooks, each with a 

 large tooth and nine smaller teeth (fig. 4e) . Setae of neuropodium and 

 anal depression region are simple capillary ones. 



Remarks: Ten species of the genus Euchone are laiown from the 

 Pacific Ocean. Euchone trisegmentata comes closest to E. rosea 

 Langerhans. Both species are the smallest laiown members of the 

 genus and each have only 17 setigerous segments, the fewest number 

 known; however, there are 4 segments to the anal depression in 

 E. rosea and only 3 in £". trisegmentata. There are 5 radioles per side 

 in E. rosea and only 3 in £". trisegmentata. The types of setae are 

 similar in both species but vary in shape and in the number of second- 

 ary teeth m the long-handled uncini and acicular hooks. 



Ecology : Euchone trisegmentata was taken from a substrate composed 

 of silts at a depth of 67.1 meters. Sixteen additional species of 

 polychaetes were present in this quantitative sample. The dominant 

 species were Glycinde wireni (88 specimens), Cossura longocirrata (69), 

 Haploscoloplos elongatus (42), and Tharyx multijilisl (38). 



Type locality: Station 5 (fig. 1), Bristol Bay area of Bering Sea, 

 56°54' north latitude and 163°45' west longitude at a depth of 67.1 

 meters. 



Type material : The holotype and six paratypes have been deposited 

 in the U.S. National Museum. 



Potamilla nsglecta (Sars) 



Sahella neglecta Sars, 1851, p. 203. 



Potamilla neglecta. — Hartman, 1948, p. 46. — Wesenberg-Lund, 1950, pp. 56-57 



pi. 10, figs. 47-48.— Berkeley and Berkeley, 1952, p. 116, fig. 238.— Pettibone 



1954, pp. 335-336, figs. 38j-n.— Uschakov, 1955, p. 409. 



Material: Stations 57(20), R-3(l); Chukchi and Beaufort Seas. 



