Polydora from Eniwetok, Majuro, and Bikini — Woodwick 
153 
tween Segment 1 and 2 is displaced posteriorly 
(on the dorsal median line), so that the carun- 
cle terminates on the level of the middle of 
Segment 2. There is no nuchal tentacle and 
only one pair of eyes; the latter are suggested 
to be the posterior median pair of the two pairs 
usually present in polydorids. 
Segment 1 is small in size compared to Seg- 
ment 2. There are no notopodial setae; neuro- 
podial setae are present but the entire parapodial 
relationship is shifted towards the mid-dorsal 
line. 
Segments 2 and 3 are well developed and 
typical. 
Segment 4 is unusual in its structure and will 
be discussed with reference to Segment 5. 
Segment 5 is modified although in over-all 
appearance it resembles the preceding and suc- 
ceeding segments, as is typical for the genus. 
There is a bundle of dorsal anterior capillary 
setae, but there is no well-developed post-setal 
lobe. The modified setae are strong, falcate hooks 
with a characteristic lined appearance (3). There 
are four on each side. The accessory setae are 
limbate. There is a well-developed neuropodium. 
Segment 4 shows an intergradation between the 
setae of Segments 3 and 5. In Segment 4 these 
setae are falcate, but have a thinner shaft and 
sharper point than those of Segment 5: they 
show the characteristic lined appearance. There 
are three on the right side of the segment and 
four on the left. These setae are comparable to 
the posterior row of winged setae of Segment 3. 
This is the most marked development of modi- 
fied setae in Segment 4 of known polydorids. 
Segment 6 has a pair of small branchiae; the 
branchiae increase in size on Segment 7, and are 
full sized on Segment 8. They are present on all 
the other segments of the 16 segment specimen. 
The neuropodial hooded hooks first appear on 
Segment 8. They are bidentate; the free point 
of the accessory tooth is very small compared to 
that of the main tooth (6). 
The specimen is named for the well-developed 
dorsal pigmentation. It has paired brown pig- 
ment stripes on the dorsal surface of each 
segment from Segments 2-13. In some of the 
anterior segments there are two pairs of stripes. 
Pseudopoly dora pigmentata occurred in hard 
coral rocks from the lagoon side of Eniwetok 
and Engebi islands of Eniwetok Atoll. At Eni- 
wetok it was associated with Opisthosyllis brun- 
nea Langerhans, and at Engebi with Dodecaceria 
laddi Hartman and Pseudopoly dor a reishi. 
Polydora tridenticulata n. sp. 
Fig. 4(2-3) 
Polydora tridenticulata n. sp. was collected at 
five stations, all on Eniwetok Atoll. A complete 
specimen of 64 segments measured 9.0 mm in 
length and 0.7 mm at the widest part. In general 
shape the worm tapers toward the posterior end. 
The prostomium is bifid and continues pos- 
teriorly as a well-developed caruncle to the 
posterior margin of Segment 3. There is no 
nuchal tentacle and the eyes are absent ( 1 ) . 
Segment 1 has well-developed notopodial 
lobes and notosetae moved towards the dorsal 
median line. 
Segment 5 is well-developed and has a definite 
indentation separating it from Segment 6. It 
projects anteriorly ventral to Segment 4 and 
posteriorly dorsal to Segment 6. The dorsal an- 
terior capillary setae project noticeably from the 
lateral surface of the segment. The large spines 
of the modified 5 th have a heavy main falcate 
stalk with two lateral teeth placed subterminally 
on opposite sides of the stalk (2). They provide 
different images as one views the setae from 
different angles. At respective angles the lateral 
teeth (a) are not visible, (b) resemble a rim- 
ming flange (3), (c) suggest a single lateral 
tooth (4), and (d) show the true situation of 
two lateral teeth on opposite sides subterminal 
to the main point. On some specimens the 
lateral teeth are worn off the anterior (first) 
spine(s), but succeeding spines and the devel- 
oping posterior embedded spines have sharp 
lateral teeth. Often in study of polydorids the 
true appearance of the modified spines of the 
5th can be seen only by freeing the developing 
embedded posterior spines in which all teeth, 
fibers, and points are unworn. The accessory 
setae are plumose with a broad terminal end. 
There is a small bundle of neuropodial setae. 
Segment 7 has the first neuropodial hooded 
hooks. They are bidentate with a well-developed 
lower tooth. 
The branchiae are first present as well-devel- 
oped structures on Segment 11; however, very 
small branchiae may be present on Segment 10. 
