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PACIFIC SCIENCE, Vol. XXII, April 1968 
water from sand which was brought to the 
surface. Associated polychaetes with this species 
include Typosyllis closterobranchia Schmarda 
and Micronephtys sphaerocirrata (Wesenberg- 
Lund) . 
remarks: The genus Euchone is now known 
from 18 species (Hartman, 1951, 1959, 1965; 
Day, 1961; Reish, I960, 1965), 9 of which 
have been reported from the Pacific Ocean. 
Previous localities from this ocean include 
Alaska, British Columbia, southern California, 
Okhotsk Sea, Kamchatka, and Japan. Euchone 
has not been collected previously from the cen- 
tral Pacific Ocean. 
Euchone eniwetokensis is distinguished from 
the majority of the species in the genus by the 
small number of branchial filaments and the 
number of segments to the anal depression. It 
comes closest to E. papillosa (Sars), known 
from the Arctic-boreal region, since both spe- 
cies have only six segments to the anal depres- 
sion. They differ in the total number of 
segments, the number of branchial filaments, 
and the length. 
type material: The holotype and one para- 
type have been deposited in the U.S. National 
Museum. 
Eabricia bikini Hartman 
Hartman, 1954?, p. 641, figs. 178 a-d. Many 
specimens were collected from white coral sand 
at Bikini Island, Bikini Atoll, in 1950; it has 
not been taken since. 
Hypicomus phaetaenia (Schmarda) 
Fauvel, 1953, pp. 447-448, figs. 236 a— 1; 
Hartman, 1954^, p. 629. eniwetok: Parry 
(L), and from Engebi (O) as reported by 
Hartman. Cosmopolitan in the warmer seas. 
Megalomma trioculatum, n. sp. 
Fig. 5 (1-10) 
Five specimens, four of which were complete, 
were collected from three islands at Eniwetok 
Atoll. Two collections of one specimen each 
were taken from a sandy bottom in 3 m of 
water on the lagoon side of Parry Island on 
June 29 and 30, 1957. The collection of three 
specimens taken from algal holdfast on Septem- 
ber 7, 1957, from the lagoon side of Engebi 
Island, was selected as type material. Specimens 
measured 7—14 mm in length including a 
branchial crown length of 2-3 mm; the holo- 
type was 14 mm in length including a branchial 
crown of 3 mm. Four specimens had 8 thoracic, 
one had 9; abdominal segments numbered from 
36 to 50 in complete specimens; the abdominal 
region consisted of 50 segments in the holo- 
type. 
Branchiae provided with 7-8 radioles per 
side, the dorsal ones provided with large, dark 
eyes at the distal end (Fig. 5, 1) ; smaller eyes 
present near the tips of the other radioles (Fig. 
5, 2); the barbs of the radioles extend to near 
the tip of the radioles. The branchial crown 
lacks pigmentation in preserved specimens. The 
collar extends from the mid-segmental line of 
the first setigerous segment anteriorly (Fig. 5, 
3), forming a pocket on either side, to the 
lateral sides which have a slight notch, and 
ventrally to produce two triangular lobes that 
nearly touch one another along the mid-ventral 
line (Fig. 5, 4). 
The notopodium of the first setigerous seg- 
ment consists of about 8 single-winged capillary 
setae; neuropodial setae are lacking. Beginning 
with thoracic segment 2, the notopodium is pro- 
vided with 3-4 single-winged capillary setae 
(Fig. 5, 3), and 5-6 subspatulate setae (Fig. 5, 
6). Thoracic neuropodium provided with about 
10 pennoned setae (Fig. 5, 7) and about 10 
uncini (Fig. 5, 8) ; the abdominal notopodium 
with about 10 uncini (Fig. 5, 9) and the neuro- 
podium with about 5 unequal double-winged 
capillary setae. The pygidium is provided with 
a dorsal triangular extension with a dorsal pair 
of eyespots. 
remarks: Twenty species have been assigned 
to the genus Megalomma (Hartman, 1959; 
Reish, 1963). Megalomma trioculatum belongs 
to that group of species which has eyes at the 
tips of all radioles. It comes closest to M. vigi- 
lans (Claparede), reported as Branchiomma 
vigilans by Fauvel (1927) from the Mediter- 
ranean Sea. They differ in the nature of the 
collar; M. trioculatum lacks the membranous 
lobes at the base of the branchiae on the dorsal 
side in M. vigilans. Megalomma vigilans is a 
much larger species than M. trioculatum; it pos- 
sesses about 150 segments, 20-25 pairs of raai- 
