. 
POLYCH.EYA FROM THE N.E. PACIFIC. 993 
EXPLANATION OF THE PLATES. 
Lettering. 
a.s. Proximal and p.s. distal half of posterior segments. 
cil.gr. Ciliated groove and enl. enlargements of the same to form accessory 
feeding organs. 
d. Dorsal lengthened sete of notopodium. 
Jr. The frilled borders of the median region. 
gl. Glandular epithelium of dorsal surface. 
lab. The two ventral lips of the mouth. 
neur. Neuropodium. 
neur. The undivided neuropodium of the first segment of the median region. 
neur.”, neur.® The double neuropodia of the second and third regions. 
not. Notopodium. 
not.', not.2, not. Notopodia of segments in median region. 
per. Peristomial collar. 
pl. Ventral plastron of anterior region. 
pro. Prostomium. 
st.t. Stumps of peristomial tentacle. 
é. Peristomial tentacle. 
w. Prolongation of the ventral plastron into median region. 
Prate I. 
Mesocetopterus taylori, sp. nu. Departure Bay, B.C. 
Fig. 1. Dorsal view, comprising the anterior and median regions with the first 
segments of the posterior region. 
2. Lateral view of same to show dorsal approximation of the borders (/%.) of 
the median segments, ete. 
3. View of lead from above to show the prostomium completely surrounded 
by the peristomium, and the slit-like mouth bordered by two ventral 
lips. 
(All three figures are drawn about twice the natural size.) 
PrateE II. 
Mesochetopterus minuta, sp.n. Cape Verde Is. 
Fig. 4. Dorsal view showing the well-developed prostomium, continuous ciliated 
groove, absence of frilled borders to median region, ete. X 20. 
Puate III. 
Mesochetopterus. 
Fig.5. Ventral view of IZ. taylori, to show end of anterior and beginning of 
median region. X 3. 
. Lateral view of posterior region in WV. taylori. X 3. 
. Lateral view otf end of median and beginning of posterior regions in 
M. minuta. X 10. 
. Hinder segments of posterior region in MW. minuta. X10. 
. Anterior view of a parapodium in the anterior region of WZ. taylori. 
Puate IV. 
Phyllochetopterus prolifica, sp. nu. 
Fig.10. A colony containing three adult worms, two of which (A, B) have just 
separated off portions (A’, 3’) of the posterior region. The rounded 
original end of the tube is seen at D. t 
Departure Bay, British Columbia. Natural size. 
11. A colony containing at least three adult worms. This shows two important 
lateral branches and a large number of short branches bearing 
apertures. That part of the system represented with close shading is the 
older, the tube-walls being opaque, and that with distinct annulations is 
newer, the transparent walls showing the worms within. (Two of these 
wornis which alinost touch each other, lie in opposite directions.) 
San Juan Archipelago, Washington. Natural size. 
(In both figures, the anterior and median regions of the worm are shown dotted, 
the posterior region very dark. The tentacles are omitted.) 
Proc. Zoou. Soc.—1914, No. LX VII. 67 
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