Polydora rickettsi, a New Species of Spionid Polychaete 
from Lower California 
Keith H. Woodwick 1 
One complete polychaete specimen and 
two fragments collected by E. F. Ricketts in 
1940 from Cape San Lucas, Lower California, 
are described here as members of a new species. 
The individuals concerned were taken from the 
tubes of Spirobranchus incrassatus Morch, a ser- 
pulid polychaete. The new species resembles 
other polydorids in some characteristics, but is 
significantly different from all known species; 
the differences are discussed below. 
Polydora rickettsi, n. sp. 
The body is flattened in shape in the anterior 
segments, becoming more rounded posteriorly. 
The posterior end is not sharply tapered but is 
only about half the width of the first few seg- 
ments. The modified 5 th segment is greatly 
enlarged. 
The complete specimen measured 10.0 mm. 
in length and included 104 segments. The 
anterior and posterior regions have a brown 
surface pigmentation, anteriorly along the lateral 
edges of the prostomium and posteriorly on all 
surfaces of the five prepygidial segments. 
The rounded prostomium (Fig. 1) with its 
lateral lines of pigment produces an anterior 
end closely resembling that of the common 
California spionid, Boccardia proboscidea Hart- 
man (1940). The greatly pronounced caruncle 
extends to the anterior margin of the modified 
5 th segment. There is a slight fold in the car- 
uncle in the region bordered by the posterior 
half of the palpal bases but there is no nuchal 
tentacle. The eyes were not visible and may have 
been faded by the preservative, although the 
1 Department of Biology, Fresno State College, 
Fresno, California. Manuscript received January 15, 
1960. 
body pigmentation was not greatly affected. 
The thick palpi are short, being equal in 
length to the first seven segments of the worm; 
they are tapered at the distal end. In dorsal 
view the peristomium is barely visible lateral 
to the palpi. 
The 1st segment lacks notosetae but the 
notopodial lobe is present. The lobe is very 
small and is crowded in at the lateral edge of 
the palpal base. The neuropodial lobe is shifted 
dorsally but remains ventral to a line created 
by the notopodial lobes of the 2nd, 3rd, and 
4th segments. These segments have notopodial 
and neuropodial lobes and setae. Their septal 
lines are erased dorsally by the presence of 
heavy longitudinal muscles paralleling the car- 
uncle. 
The enlarged 5 th segment has a heavy mus- 
culature which overlaps most of segment 6 and 
part of segment 7 dorsally ( Fig. 1 ) . Anteriorly 
it crowds segment 4 and has a small anterior 
roll or cuff in that region. The heavy muscle 
bands associated with the specialized setae orient 
from the anterior lateral portion of the seg- 
ment to the posterior median line. The an- 
terior dorsal capillary setae precede the row of 
specialized setae. The latter have a main fal- 
cate tooth and a sharply curved pointed ac- 
cessory tooth. There also is a flange located 
laterally on the main tooth at the level of the 
accessory tooth (Figs. 2, 3, 4). The companion 
setae are smaller plumose setae (Fig. 6). There 
is a very poorly developed bundle of neuropo- 
dial capillary setae. These are difficult to see 
and ordinarily are not taken when the special- 
ized setae are removed for further study. 
The 6th segment is about half the size of the 
8th and the setal lobes are poorly developed. 
FIGS. 1-7. Polydora rickettsi, n. sp. 1, Anterior end, dorsal view (X 144); 2, 3, 4, specialized setae of modi- 
fied 5th segment, new, worn, greatly worn, each at a different angle (X 555); 5, ventral hooded hooks from 
the 7th segment (X 900); 6, companion setae from modified 5th segment (X 1800); 7, pygidium, in poste- 
rior dorsal view (X 120). 
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