Poly dor a from Eniwetok, Majuro, and Bikini — Woodwick 
155 
Branchiae are present only as far as Segment 26 
on a complete 64-segment specimen. 
Posterior notopodial spines are lacking, but 
a few long thin capillary setae are present in 
each notopodium. 
The pygidium is slightly wider than the last 
segment. It is not of the flared-disc shape, but 
has a heavy cuff of refractile tissue. The cuff 
is as long as 2 l /i pre-pygidial segments. The 
pygidium has a dorsal notch ( 3 ) . 
Polydora tridenticulata was found at stations 
on the lagoon and ocean sides of Japtan, and 
from the lagoon side of Rigili and Engebi is- 
lands of Eniwetok Atoll. This form is an in- 
habitant of coral rock and by setal structure is 
likely a boring form. It was associated with 
Pseudonereis anomala Gravier at two stations, 
and at separate stations with Palola siciliensis 
(Grube) and Haplosyllis spongicola (Grube). 
Polydora tridenticulata is similar to Polydora 
anoculata, P. giardi, P. flava, and P. caeca. It is 
like the first two in gill arrangement, and simi- 
lar to the others in appearance of the setae of 
the fifth. However, unlike the last two, P. 
tridenticulata lacks posterior notopodial spines. 
Tripolydora, new genus 
Type T. spinosa , new species 
The fifth segment is modified as in Polydora, 
Pseudopoly dor a, and Boccardia . The general ap- 
pearance of the worm and of the fifth segment 
indicates closer affinities with Pseudopoly dora 
than with the other two genera. It differs from 
all three in that the neuropodial hooded hooks 
begin on Segment 9 and are tridentate. Branchiae 
are present on segments. 
Tripolydora spinosa, n. sp. 
Fig. 4 (6-9) 
Tripolydora spinosa n. sp. was found at two 
stations, both on Eniwetok. Complete specimens 
of 25, 25, and 40 segments measured 1.5, 1.6, 
and 3.0 mm respectively. The body is tapered 
slightly in the posterior one-third. The rounded 
prostomium continues posteriorly as a heavy 
caruncle reaching to the posterior margin of the 
third segment (6). The palps are retained on 
some specimens; on a 25 segment individual 
they extend to the middle of the body. No eyes 
are visible. 
Segment 1 is poorly developed, lacking noto- 
setae and post-setal lobes. The neuropodium has 
shifted towards the dorsal midline, and the 
entire segment is but a vestige compared to 
Segment 2 and succeeding segments. 
Segment 2 has the first branchiae, which are 
present also on Segments 3, 4, and 5 in a re- 
duced size. Fully-developed branchiae begin on 
Segment 6. The branchiae are present posteriorly 
on all but a few pre-pygidial segments. 
Segment 5 is a modified segment but resem- 
bles that of members of Pseudopolydora as, in 
general, it is not quickly separable from the 
preceding and succeeding segments on the basis 
of shape, branchiae, and setal components. It 
does, however, have two or three modified spines 
on each side. The spines are heavy-shafted, 
having a semifalcate tooth at one side sur- 
rounded by a subterminal flange with a central 
indentation ( 7 ) . The neuropodium is well 
developed, having both setae and a post-setal 
lobe. 
The neuropodial hooded hooks are important 
diagnostic characteristics with respect to their 
structure and location. They are tridentate (8); 
other forms with a modified fifth segment have 
unidentate or bidentate hooks. These hooks 
appear first in Segment 9, in a posterior row 
accompanied by an anterior row of winged 
setae; the latter are present anteriorly as far as 
Segment 4 and posteriorly to Segment 10. At 
the anterior and posterior limits they intergrade 
with capillary setae. 
Posterior notopodial setae are present as a 
heavy bundle of fine needles in the last 4 seg- 
ments of a 30-segment specimen (9). The pre- 
ceding four segments intergrade with the general 
setal arrangement. 
The pygidium is smaller in diameter than 
the pre-pygidial segment; it has two ventral lap- 
pets and two less distinct dorsal lappets. Its 
shape is not like the flaring cup typical of most 
Fig. 3. 1-3, Pseudopolydora reishi, n. sp. 1, Anterior end, X300; 2, setae of fifth, X1000; 3, pygidium, 
X300. 4-6, Pseudopolydora pigmentata, n. sp. 4, Anterior end, X250; 3, setae of fifth, X1000; 6, hooded 
hooks, X2400. 
